Arcade and game design, word by word

A way of combining colours where a new image's brightness is added to whatever is already on screen, so overlapping areas get lighter rather than covered. It is why sparks, fireworks and glowing trails look like light: stack enough of them and the middle turns almost white.

See also Particle effect, Shader, Phosphor.

A thumb-sized stick that reports how far it is pushed, not just which way, so a game can tell a gentle nudge from a full tilt. That let 3D games offer walking and running on one control, and made smooth steering and camera movement possible on a gamepad.

See also Dead zone, Gamepad, D-pad. More in the 16-Bit Hall.

Techniques that soften the jagged, staircase edges that appear when a smooth line or curve is drawn with square pixels. The computer blends edge pixels with the colours behind them to fake a smoother shape. Pixel art usually avoids it on purpose, because the crisp, hard edge is part of the look.

See also Pixel, Pixel art, Resolution.

A type of colour CRT screen that uses a fine sheet of vertical wires, rather than a perforated plate, to guide the electron beams onto stripes of red, green and blue phosphor. It let more light through, giving brighter pictures, and on large screens you can sometimes spot one or two faint horizontal support wires.

See also Shadow mask, Cathode-ray tube, Phosphor. More in the CRT simulator.

A small program that runs inside a web page, usually through a plugin. Java applets were a common way to put games and interactive demos on early websites, though they were often slow to start. Browsers later dropped support for these plugins in favour of built-in technologies such as HTML5.

See also Plugin, Browser game, HTML5. More in the Early Web Hall.

An online shop built into a phone, tablet or console where people find, download and update software. Stores changed how small games reached players: one developer could publish worldwide without a box or a shop shelf, but standing out among thousands of new releases became the hard part.

See also Free-to-play, Hyper-casual, Indie game. More in the One-Tap Hall.

A public room full of coin-operated games, from video cabinets to pinball tables, where people played, watched and compared scores. Arcades were social places: you learned by standing behind better players, and the high-score table made a local name for anyone who topped it.

See also Arcade cabinet, Coin-op, High score. More in the Golden Arcade.

The tall wooden or metal box that holds an arcade game: the screen, the control panel, the speakers, the coin door and the circuit boards inside. The painted sides, the marquee and the bezel art were designed to catch the eye of passers-by from across a busy room.

See also Upright cabinet, Cocktail cabinet, Marquee. More in the Golden Arcade.

Playing the notes of a chord one after another instead of all at once. Early sound chips had only a few channels, so composers cycled through chord notes very quickly on a single channel to suggest harmony. The result is the fast, bubbling warble heard in a lot of chiptune.

See also Chiptune, Channel (sound), Sound chip. More in the Chip Synth.

The shape of a screen or image, written as width compared with height, such as 4:3 or 16:9. Old televisions and arcade monitors were 4:3, and some cabinets turned the monitor on its side for a tall picture. Showing an old game on a different shape means stretching it or adding borders.

See also Resolution, Safe area, Bezel.

The short demonstration an arcade cabinet plays when nobody is using it: the title, a few seconds of the game playing itself and the high-score table, on a loop. It was the machine's way of advertising itself across a noisy room, and it often taught the controls better than the instructions printed on the panel.

See also Arcade cabinet, High score. More in the Vector Hall.

A colour glitch on some 8-bit computers, most famously the ZX Spectrum, where colour was stored for each block of 8 by 8 pixels rather than for each pixel. When a moving character crossed a differently coloured background, the whole block changed colour around it. Many artists kept play areas mostly one colour to hide it.

See also Palette, Bit depth, Home computer. More in the Palette toy.

A strategy game where you choose and arrange a team before each round, then watch the contest play out by itself. The skill is all in the planning: which pieces to pick, how to combine them and where to place them. The genre grew out of player-made mods before becoming a category of its own.

See also Turn-based, Mod. More in the Indie Pocket Hall.

The frame around a screen. On arcade cabinets it was often a printed sheet of glass or plastic, decorated with artwork and instructions, that hid the edges of the monitor. Emulators and retro collections sometimes draw a bezel around the picture to fill the empty space on wide screens.

See also Arcade cabinet, Aspect ratio, Marquee.

The number of bits used to store each pixel's colour, which sets how many colours can appear. One bit gives two colours, four bits give sixteen and eight bits give 256. Low bit depths forced artists to choose palettes carefully and to use tricks such as dithering to suggest shades they did not have.

See also Palette, Dithering, Pixel. More in the Palette toy.

An image stored as a grid of pixels, each with its own colour value, as opposed to a vector drawing made of lines and shapes. Bitmaps hold fine detail well but turn blocky when enlarged, which is why pixel art is usually scaled up by whole numbers to stay crisp.

See also Pixel, Sprite, Vector display.

A piece of hardware dedicated to copying and combining blocks of image data in memory very quickly, so the main processor does not have to. The name comes from block image transfer. Machines such as the Commodore Amiga used one to move large graphics around the screen smoothly.

See also Sprite, Frame buffer, Bitmap.

A big, tough opponent at the end of a level or section, usually with its own music, a health bar and a pattern of moves to learn. A boss acts as a test of everything the level has taught, and getting past one tends to mark a clear step forward in the game.

See also Pattern (arcade), Health bar, Level (stage).

A game where you steer a paddle along the bottom of the screen to bounce a ball into rows of bricks, clearing each one it touches. Miss the ball and you lose a life. The idea dates back to 1970s arcades and is still a favourite first project for people learning to make games.

See also Paddle controller, Collision detection, Power-up.

A game that runs inside a web browser with nothing to install. Early ones relied on plugins such as Flash and Java, while modern ones use built-in technologies like HTML5 canvas, WebGL and WebAssembly. Being one link away from playing made them easy to share in schools, offices and forums.

See also HTML5, Canvas, Plugin. More in the Early Web Hall.

A mistake in a program that makes it behave in a way its makers did not intend, from a character walking through a wall to the whole game freezing. Some bugs became well known and even loved by players, and a few were later kept on purpose as features.

See also Glitch, Speedrun, Easter egg.

A computer that other people could dial into over a phone line with a modem, usually one caller at a time, to read messages, swap files and play simple text games. Before the web was common, bulletin boards were one of the main ways to pass around shareware and meet other players.

See also Shareware, Text adventure. More in the 16-Bit Hall.

Pressing buttons as fast as possible, often without a plan. Some games ask for it on purpose, such as athletics games where rapid tapping makes a runner go faster. In other games it is simply how beginners play, and designers often make sure mashing gets some results so newcomers still have fun.

See also Combo, Input lag.

An HTML element that gives a web page a blank rectangle a program can draw on, pixel by pixel or with shapes, many times a second. It became the standard surface for browser games once plugins faded, and it can be drawn on with simple 2D commands or with WebGL.

See also HTML5, WebGL, Browser game.

A plastic case holding a circuit board with the game stored on ROM chips, which plugs straight into a console or computer. Cartridges loaded almost instantly and were hard to damage, but chips cost more than discs, so games had to fit into very little space. Some added extra chips for saving or graphics.

See also ROM, Console, Password save.

A game designed to be easy to pick up, with simple controls and short sessions, so it fits into a tea break. Puzzle, card and match-three games are typical. Casual games reached many people who did not think of themselves as players, first through web portals and later on phones.

See also Match-three, Hyper-casual, Portal (game website). More in the Flash Hall.

The deep glass tube behind old televisions and arcade monitors. An electron beam sweeps across the inside of the screen line by line, lighting up a coating of phosphor as it goes. Its soft glow, visible scan lines and slight curvature are part of how old games were meant to look.

See also Scan line, Phosphor, Shadow mask. More in the CRT simulator.

A run of linked actions where each one sets off the next, such as cleared blocks letting others fall into fresh matches. Puzzle and score-chasing games usually reward chains with growing points, so planning several steps ahead pays off more than quick single moves.

See also Combo, Score multiplier, Falling-block puzzle.

One independent voice a sound chip can play at a time. A chip with three channels could play a melody, a bass line and a drum part together, and nothing more. Composers squeezed in extra parts by switching a channel between jobs very quickly, too fast for the ear to notice.

See also Sound chip, Noise channel, Arpeggio. More in the Chip Synth.

A secret input, such as a button sequence or a typed word, that changes a game in ways the normal rules do not allow: extra lives, a level select or odd visual effects. Many began as shortcuts the developers used for testing, which were then left in and shared between players.

See also Easter egg, Extra life, Password save.

A point partway through a level where the game remembers your progress, so if you lose a life you restart there instead of at the beginning. Placing checkpoints is a balancing act: too far apart and the game feels harsh, too close together and the tension disappears.

See also Respawn, Save point, Difficulty curve.

Music made with, or in the style of, the sound chips in old consoles and computers. Limited channels and simple waveforms such as square and triangle waves give it a bright, buzzy sound. It is now a music scene of its own, with artists composing on original hardware and trackers.

See also Sound chip, Square wave, Tracker. More in the Chip Synth.

A game that copies another game's main idea closely, often with new graphics and a new name. Clones were common in early arcades and on home computers, where popular hits were quickly redone for other machines. Some clones improved on the original, and several genres began as a wave of them.

See also Remake, Port.

A table-shaped arcade cabinet with the screen facing up under a glass top, so players sit across from each other. In two-player games the picture flips each turn to face whoever is playing. They suited cafés, restaurants and hotel lobbies, where a low table fitted better than a tall machine.

See also Arcade cabinet, Upright cabinet. More in the Golden Arcade.

Short for coin-operated: any machine that starts when you put a coin in, from arcade video games to pinball tables. The coin set the rhythm of play, so arcade games were designed to be learned quickly and to end fairly soon, which kept the queue moving.

See also Credit (arcade), Arcade, Free play. More in the Golden Arcade.

The code that works out when two things in a game touch, such as a character landing on a platform or a ball reaching a brick. Games usually check simple invisible shapes rather than exact pixels, which is faster and explains why a near miss can sometimes count as a hit.

See also Hitbox, Physics engine, Game loop.

A setting that changes a game's colours, or adds shapes and patterns, so players who see colour differently can still tell important things apart. Red and green are the pair most often confused, so a good mode never relies on colour alone to carry meaning.

See also Reduced motion, Palette. More in the Daily Puzzle Hall.

A series of moves performed in quick succession that the game counts together, usually for bonus points or a bigger effect. An on-screen counter keeps track, and it resets if you pause too long or make a mistake. Learning combos is a large part of mastering many action and puzzle games.

See also Chain, Score multiplier, Button mashing.

A way of sending a whole colour picture down a single cable, with brightness and colour mixed together. It was cheap and common on old consoles, but colours bled into each other slightly. Some artists used that blur on purpose, letting dithered patterns smudge into extra shades on screen.

See also Cathode-ray tube, Dithering, Resolution.

A computer built mainly for playing games, usually connected to a television and controlled with gamepads. Unlike a home computer, a console is the same inside for every owner, so developers can tune a game exactly to its hardware and know it will run the same in every home.

See also Gamepad, Cartridge, Home computer.

An option, after game over, to keep playing from where you stopped instead of starting again. In arcades a continue usually cost another coin, with a countdown on screen to decide. Home games often gave a set number of continues to stretch the challenge out.

See also Credit (arcade), Game over, Lives.

The part of an arcade cabinet where the joysticks, buttons and other controls are mounted, usually angled towards the player at waist height. Its layout told you a lot about a game before you played: one stick and one button meant something simple, while a row of six buttons suggested something more involved.

See also Joystick, Microswitch, Arcade cabinet.

Short for cooperative play: two or more people playing on the same side towards a shared goal, rather than against each other. Arcade co-op games let a friend join in by adding a coin, and later games added online co-op so players in different places could team up.

See also Arcade, Continue.

A brief grace period, usually a tenth of a second or so, during which a platformer still lets you jump after you have run off the edge of a ledge. Players never notice it, which is the point: without it, jumps that felt right would fail, and the game would seem unfair.

See also Jump buffering, Game feel, Platformer.

A relaxed game with gentle goals, soft visuals and little or no failure, built around activities such as farming, decorating or tidying. There is no timer pushing you along, and progress comes from small routines. The appeal is calm and comfort, which is why many people play them to unwind.

See also Casual game, Idle game, Merge game. More in the Daily Puzzle Hall.

One paid play on an arcade machine, shown as a number on screen once coins go in. Some games asked for one credit per player, and some gave extra credits for larger coins. With free play switched on, the machine starts without needing any credits at all.

See also Coin-op, Continue, Free play. More in the Golden Arcade.

A short scene you watch rather than play, telling part of the story between levels or at key moments. Early arcade games used brief cartoon interludes between stages, and later games grew them into full film-like sequences. Most modern games let you skip them.

See also Level (stage), Attract mode.

A puzzle or level that changes once a day and is the same for everyone playing it. Because all players face identical conditions, results can be compared fairly and shared without spoiling the answer. Many daily games build each puzzle from a random seed based on the date.

See also Random seed, Leaderboard, Deterministic. More in the Daily Puzzle Hall.

A small area around a stick's centre position where movement is ignored. Sticks rarely rest perfectly centred, so without one, characters or cameras would slowly drift on their own. Too large a dead zone makes controls feel sluggish, and too small a one lets the drift come back.

See also Analogue stick, Gamepad, Input lag.

A community of programmers, artists and musicians who make demos: short real-time shows of graphics and music that push computers far beyond what seemed possible. It grew out of home computer culture in Europe, and members still gather at events to compete over who can squeeze the most into tiny files.

See also Home computer, Tracker, Shader.

Describes a system that always gives the same result from the same starting point and the same inputs. A deterministic game can replay a whole match just by recording button presses, and can give everyone exactly the same puzzle. Hidden differences in timing or rounding can quietly break it.

See also Random seed, Replay, Fixed timestep.

How a game's challenge changes as you progress. A good curve introduces one idea at a time and raises the pressure gradually, with small breathers after the hard parts. A curve that climbs too steeply loses new players, and one that stays flat loses experienced ones.

See also Tutorial, Level (stage), Checkpoint.

Arranging dots of two colours in a pattern, such as a checkerboard, so that from a distance the eye blends them into a third colour or a smooth gradient. It let artists suggest many more shades than a limited palette actually held, and the textured look became part of many styles.

See also Palette, Bit depth, Pixel art. More in the Palette toy.

Short for directional pad: a flat, cross-shaped button pressed with the thumb to move up, down, left or right. It replaced the joystick on handhelds and gamepads because it was thin, sturdy and precise, and it is still the preferred control for many 2D games.

See also Gamepad, Joystick, Analogue stick. More in the Golden Arcade.

Changing the speed of a movement over time so it starts or stops gradually instead of at a constant rate. A menu that slows as it settles, or a jump that hangs at its peak, feels more natural because real objects rarely move at a steady speed. Designers choose from named curves such as ease-in and ease-out.

See also Juice, Squash and stretch, Game feel.

A hidden message, room or joke placed in a game for curious players to find. A well-known early example is Adventure on the Atari 2600, whose programmer hid his own name in a secret room because game boxes did not credit their makers. Easter eggs reward exploring beyond the obvious.

See also Cheat code, Bug.

A program that imitates an old computer or console in software, so its games can run on modern devices. Accuracy is the hard part: matching the original timing, sound and quirks exactly. Emulators are central to preservation, since original hardware wears out and becomes harder to find.

See also Preservation, ROM, Port. More in the Revived Wing.

A game where your character runs forward on its own and you only steer, jump or slide past obstacles for as long as you can. There is no finish line: the speed keeps rising until the run ends, and your score is the distance covered. Its one-touch controls suited phones well.

See also One-button game, Procedural generation, High score. More in the One-Tap Hall.

An additional try awarded during play, usually for reaching a score threshold or picking up a special item. On many arcade machines the operator could choose the score needed. Earning one gives players a clear target to aim for and a welcome moment of relief.

See also Lives, High score, Power-up.

A puzzle game where pieces drop from the top of a well and the player moves and rotates them to fill complete rows or make matches, which then clear away. The pieces fall faster as you progress, and the run ends when the stack reaches the top.

See also Puzzle game, Chain, Match-three.

Running a game's logic in equal slices of time, for example sixty updates a second, whatever speed the screen is drawing at. It keeps physics, jumps and replays consistent across fast and slow devices, while drawing can still happen as often as the hardware allows.

See also Game loop, Deterministic, Frame rate.

A way of making sound by using one waveform to rapidly bend the pitch of another, which produces rich, metallic or bell-like tones from very little hardware. Yamaha FM chips supplied the music for many arcade boards and home computers, as well as the Sega Mega Drive.

See also Sound chip, Chiptune, Channel (sound). More in the Chip Synth.

One still image in a sequence that, shown quickly one after another, creates the look of movement. In games it also means one cycle of the game loop: read input, update, draw. Many arcade games did all their work in a sixtieth of a second, so actions are often measured in frames.

See also Frame rate, Game loop, Frame buffer.

A block of memory holding the colour of every pixel on screen, which the display hardware reads out to draw the picture. Games draw the next image into it, and many use two buffers, showing one while drawing the other, so players never see a half-finished frame.

See also Frame, Vertical blank, Bitmap.

How many new images a game shows each second, measured in frames per second. Higher rates make motion smoother and controls more responsive. Many older console games ran at about 60 on NTSC televisions and 50 on PAL ones, so some European versions played noticeably slower.

See also Frame, Refresh rate, Input lag.

An arcade setting that lets a machine run without coins, so anyone can simply press start. Operators used it for parties, events and testing, and many museum and home cabinets are left on it permanently. The game itself is unchanged: only the credit check is skipped.

See also Credit (arcade), Coin-op, Arcade cabinet.

A way of selling games in which the game costs nothing to download and play, and the makers earn from optional purchases or advertising inside it. It became the dominant business on phones in the 2010s, and it changed design: games were built to be returned to every day rather than finished once.

See also Hyper-casual, App store, Casual game. More in the Indie Pocket Hall.

The moment-to-moment sense of how a game responds under your hands: how quickly a character starts and stops, how high it jumps, how a landing looks and sounds. Two games with identical rules can feel completely different, and most of the difference lives in tiny timings players never consciously notice.

See also Juice, Coyote time, Input lag.

An event where people make a small game from scratch in a fixed, short time, often a single weekend, usually around a theme announced at the start. Jams reward small ideas finished well, and a surprising number of later full-sized indie games began as a rough prototype built in forty-eight hours.

See also Indie game, Homebrew, Open source.

The cycle at the heart of every video game program: read the player's input, update the world by a small step, draw the result, then do it all again, many times a second. Designers also use the phrase for the repeated cycle of play itself, such as explore, collect, upgrade and repeat.

See also Frame, Fixed timestep, Frame rate.

The message shown when a run ends, usually after the last life is lost or the timer runs out. In the arcade it was the moment the machine asked for another coin, and many cabinets showed a short countdown to continue first. Today it more often leads straight to a retry button.

See also Continue, Lives, Credit (arcade).

A controller held in both hands, with a directional pad or stick under the left thumb and action buttons under the right. Later pads added shoulder buttons and twin analogue sticks. Modern browsers can read a connected gamepad directly, so a web game can be played from the sofa as easily as from a desk.

See also D-pad, Analogue stick, Shoulder button.

A see-through replay of an earlier run, often your personal best, that races alongside you without getting in the way. Because it follows exactly the same route and timing each time, it shows where you are gaining or losing, which makes it a quiet but very effective teacher in racing and time-trial games.

See also Time attack, Personal best, Replay.

A visible or audible mistake in a game, such as scrambled graphics, a character stuck inside a wall or a sound that repeats. Glitches come from bugs, overloaded hardware or corrupted data. Some became famous in their own right, and speedrunners sometimes use them deliberately to skip whole sections of a game.

See also Bug, Speedrun, Sprite flicker.

In a game, a steady downward pull added to a character's speed every frame, so that jumps rise, slow, peak and fall. Designers tune it freely rather than copying real physics: many platformers pull harder on the way down than on the way up, which makes jumps feel snappy instead of floaty.

See also Platformer, Physics engine, Game feel.

Feedback you feel rather than see or hear: a buzz, click or rumble from a controller or phone. Better vibration motors in phones made it possible to give a short, crisp tap for a button and a softer pulse for a landing. Like other effects, haptics work best when quiet, and good games let you switch them off.

See also Juice, Touch screen, Gamepad. More in the Indie Pocket Hall.

A strip on screen, usually near the top, that shrinks each time a character takes a knock and shows how much more it can take before losing a life. It replaced the all-or-nothing single touch of many early games, letting players recover from mistakes and judge risk at a glance.

See also HUD, Lives, Boss.

The best score recorded on a game, shown at the top of the screen and in a ranked table. In arcades the table lived on the machine itself, so beating the local high score was a public act, and the list of initials gave players a reason to keep coming back to the same cabinet.

See also Initials, Leaderboard, Personal best. More in the Vector Hall.

An invisible shape, usually a simple rectangle or circle, that a game uses to decide whether two objects are touching. It rarely matches the drawing exactly. Generous games make the player's hitbox a little smaller than the sprite, so near misses feel lucky rather than unfair, and the game earns the player's trust.

See also Collision detection, Sprite, Pixel.

A tiny freeze, often just a few frames long, at the moment two things collide, such as a ball meeting a bat or a hammer striking a peg. The pause gives the eye time to register the impact and makes it feel heavier. Players rarely notice it is there, but they notice when it is missing.

See also Juice, Screen shake, Game feel. More in the Indie Pocket Hall.

Software made by hobbyists rather than licensed studios, usually for an old console or handheld that its makers stopped supporting long ago. Homebrew developers work within the original hardware limits, and some still release new cartridges for decades-old systems, complete with printed boxes and manuals.

See also Emulator, Cartridge, Demoscene.

A small, affordable computer of the late 1970s and 1980s that plugged into the family television and was meant for the home rather than the office. Machines such as the ZX Spectrum, Commodore 64 and BBC Micro came with a programming language built in, so many children learned to code by typing in games.

See also Type-in program, Cartridge, Attribute clash. More in the Golden Arcade.

The fifth major version of the language web pages are written in, together with the browser features that arrived around it, including the canvas element and built-in audio and video. It let browsers run games without plugins, and it is the main reason games made for the web now play on phones as well as computers.

See also Canvas, Browser game, Plugin. More in the Flash Hall.

The layer of information drawn over the game world: score, lives, timer, health bar or map. The name comes from aircraft displays that project readings onto the glass so the pilot can keep looking ahead. A good HUD is readable at a glance and stays out of the way of the action.

See also Health bar, Safe area, Lives.

A kind of phone game built around one simple mechanic that anyone can understand within seconds, usually with a single tap or swipe and almost no menus. The name was coined around 2017. These games were cheap to make, quick to test and mostly paid for by advertising shown between short rounds.

See also Casual game, One-button game, Free-to-play. More in the Indie Pocket Hall.

A game in which numbers keep growing even when you are not playing: you click or tap to earn a resource, spend it on things that earn more by themselves, and come back later to find a bigger pile. The pleasure is in watching growth compound and planning the next upgrade.

See also Casual game, Browser game, Free-to-play.

A game made by a small, independent team or a single person, without a large publisher paying for it or directing it. Cheap engines and digital shops made indie games far easier to make and sell from the late 2000s onward, and many took up styles big studios had left behind, such as pixel art.

See also Game jam, Pixel art, Homebrew. More in the Indie Pocket Hall.

The tendency of a moving object to keep moving until something slows it down. In games it means a ship or character that drifts after you let go of the controls, so you have to plan your stops in advance. Asteroids made its ship glide this way, and the handling became much of the challenge.

See also Vector display, Gravity, Game feel. More in the Vector Hall.

The three letters a player enters beside a score on an arcade high-score table, chosen one at a time with the joystick and button. Three letters fitted neatly into a short table on screen, and regulars at a local arcade often became known by the letters they left behind.

See also High score, Leaderboard, Attract mode. More in the Vector Hall.

The delay between pressing a control and seeing the result on screen. It builds up from the controller, the game's own processing and the display, and modern flat televisions can add noticeably more than old tube sets. Even a few hundredths of a second can make precise jumps feel sluggish.

See also Frame rate, Refresh rate, Cathode-ray tube.

A way of drawing a television picture in two passes: first every odd line, then every even line, so the full image is built from two half-pictures in quick succession. It saved broadcast bandwidth. Many older consoles drew the same lines on every pass instead, which is part of why their pictures show visible gaps between lines.

See also Scan line, Cathode-ray tube, Refresh rate. More in the CRT simulator.

A simple multiplayer browser game where you join a big shared arena instantly, with no download or account, steer with the mouse and try to grow larger than everyone else. The name comes from the .io web addresses the early hits used. Rounds are short, and losing just means starting small again.

See also Browser game, Mouse, Leaderboard. More in the Indie Pocket Hall.

A way of drawing a 3D world on a flat screen from above and at an angle, without perspective, so objects stay the same size wherever they stand. Pixel artists usually draw its lines rising one pixel for every two across, which keeps the edges clean. It gave depth to strategy and puzzle games long before true 3D was cheap.

See also Top-down view, Tile map, Pixel art.

A lever the player pushes in a direction to steer. A classic arcade joystick is a short shaft with a ball top, held centred by a spring, with four microswitches underneath that click as it moves. Some games limit it to four directions with a plastic gate, while others allow all eight.

See also Microswitch, D-pad, Analogue stick. More in the Golden Arcade.

All the small responses that make an action feel good without changing the rules: a squash on landing, a puff of particles, a brief pause or shake, a rising note for each point in a combo. Good juice is used sparingly. Too much tires the eyes and hides what is actually happening in the game.

See also Squash and stretch, Screen shake, Hit pause. More in the Indie Pocket Hall.

A small forgiveness trick in which a game remembers a jump pressed slightly too early, just before landing, and performs it the moment the character touches the ground. Without it, players who pressed at what felt like the right time would see nothing happen. Like coyote time, it works because nobody notices it.

See also Coyote time, Game feel, Platformer.

The link between a key or button and the action it performs, such as space to jump. Games that let players rebind keys are easier to play on unusual keyboards, for left-handed players and for anyone using adaptive controllers, which makes remapping one of the simplest and most useful accessibility settings.

See also WASD, Gamepad, Colour-blind mode.

A flat screen that makes pictures by twisting tiny crystals to block or pass light. Early handheld games used fixed LCD shapes printed into the glass, so each figure could only appear in a few set positions. Later LCD panels became the full-colour screens of phones, laptops and modern televisions.

See also Cathode-ray tube, Pixel, Input lag.

A ranked list of the best scores or times, shared between players. Arcade tables only knew one machine, while online leaderboards can compare everyone in the world, or just a group of friends. Many daily games keep a fresh board for each day, so a new player always starts on equal footing.

See also High score, Daily challenge, Personal best.

A tool for building and changing a game's levels, placing walls, platforms, items and hazards on a grid and then testing the result. Some studios kept their editors private, while others shipped them inside the game, turning players into designers and giving those games a long second life of shared creations.

See also Level (stage), Tile map, Mod.

One section of a game, with its own layout and usually a clear start and finish, such as a single maze or a stretch of platforms ending at a flag. Levels let a game teach one idea at a time and raise the difficulty in steps. The word can also mean a character's rank in role-playing games.

See also Level editor, Difficulty curve, Boss.

The number of attempts a player has left before the game ends, often shown as small icons in a corner. Arcade machines gave a handful per coin so that a session lasted a few minutes. Earning an extra life at a set score became a common reward, and losing the last one means game over.

See also Extra life, Game over, Continue.

A piece of music written to repeat seamlessly, so its end flows straight back into its start. Small memory budgets meant a level might have well under a minute of music, played over and over. In arcades the word also means the point where a game runs out of new stages and starts again from the first.

See also Chiptune, Tracker, Level (stage). More in the Chip Synth.

A 3D style built from a small number of flat-shaded polygons, so faces and edges stay visible. It began as a hardware limit in early 3D games and returned in the 2010s as a deliberate look: cheap to render on phones, readable at any size and pleasantly handmade, like a model on a table.

See also Polygon, Wireframe, Pixel art. More in the Indie Pocket Hall.

The lit sign across the top of an arcade cabinet, showing the game's name and artwork, usually printed on translucent plastic with a lamp behind it. It was the first thing a player saw from across a crowded room, so marquees were bold, bright and easy to read from a distance.

See also Arcade cabinet, Bezel, Attract mode. More in the Golden Arcade.

A puzzle game where you swap or move pieces on a grid to line up three or more of the same colour or shape, which then vanish and let the pieces above fall into the gaps. New matches made by falling pieces create chains, and planning for them is where most of the skill lies.

See also Chain, Puzzle game, Casual game.

A game played inside a network of corridors, where the challenge is finding routes, collecting items and staying clear of rivals that roam the same passages. Pac-Man is the best-known example. Because the whole maze usually fits on one screen, players can plan ahead and learn how the pursuers behave.

See also Pattern (arcade), Top-down view, Tile map. More in the Golden Arcade.

A game built around combining two matching items to make a single better one, then combining those in turn. Some use a board you drag pieces around, others drop items into a container where touching pairs join up. The pleasure is in the small click of two things becoming one, repeated toward an ever larger result.

See also Match-three, Idle game, Cozy game. More in the Daily Puzzle Hall.

A small switch that clicks on with very little movement and springs back by itself. Arcade joysticks and buttons use them because they are cheap, reliable and give a crisp click you can feel. A typical joystick has four, one for each direction, and pushing diagonally presses two at once.

See also Joystick, Control panel, Arcade cabinet. More in the Golden Arcade.

A change to an existing game made by players rather than its original makers, from a new costume or level to a whole new game built on the old engine. Some studios welcome mods and release tools to make them. A few mods became so popular that they grew into full games of their own.

See also Level editor, Open source, Homebrew.

A hand-held pointing device that moves a cursor as it slides across a desk. It made new kinds of game possible on computers and in early browsers: point-and-click adventures, drag-and-drop puzzles and games where you simply steer toward the pointer. Its precision is very different from a joystick's sense of direction.

See also Point-and-click, Trackball, Browser game. More in the Early Web Hall.

A control that switches a game's sound off. In browser games it became a standard convention to put a mute button somewhere on screen, since people often played at school, at work or late at night. Modern browsers also hold back a page's sound until the player has clicked or tapped on it.

See also Chiptune, Key binding, Reduced motion.

A sound-chip channel that produces hiss rather than a musical note, made by switching the output on and off in a pseudo-random pattern. Changing how fast it switches makes the hiss lighter or rougher. Composers used it for drums and cymbals, and sound designers for crashes, waves, engines and rushing wind.

See also Square wave, Triangle wave, Sound chip. More in the Chip Synth.

A game controlled entirely with a single input: one key, one button or one tap on the screen. All the depth has to come from timing, such as when to press, how long to hold and when to let go. The format suits phones well and makes a game possible to learn in seconds.

See also Endless runner, Hyper-casual, Touch screen. More in the One-Tap Hall.

Software whose source code is published under a licence that lets anyone read it, change it and share their changes, within the licence's conditions. Open-source engines, tools and remakes keep many old games playable after their original makers have moved on, because the code no longer depends on a single company.

See also Preservation, Emulator, Remake. More in the Revived Wing.

A controller with a knob that turns, used to move a bat back and forth along one edge of the screen. Inside is a variable resistor: the further the knob turns, the more the reading changes, so the bat's position follows your hand directly and precisely. Bat-and-ball games were built around it.

See also Spinner, Brick-breaker, Analogue stick. More in the Vector Hall.

The fixed set of colours a game or machine can show, or the chosen subset an artist works with. Older hardware might offer a few dozen colours and only let a handful appear on screen at once, so artists picked carefully and used tricks such as dithering to suggest more than were really there.

See also Bit depth, Dithering, Attribute clash. More in the Palette toy.

A way of suggesting depth in a 2D game by moving background layers more slowly than the foreground as the view scrolls, just as distant hills seem to drift past more slowly than nearby fences from a train window. It became a signature of 16-bit side-scrollers and is still widely used today.

See also Side-scroller, Pseudo-3D, Tile map. More in the 16-Bit Hall.

The part of a text adventure that reads what the player types, such as TAKE LAMP or GO NORTH, and works out what it means. Many early parsers understood only two words, a verb and a noun. Later ones handled longer sentences, but every parser had limits, and finding the right phrasing was part of the puzzle.

See also Text adventure, Point-and-click, Easter egg. More in the Revived Wing.

A visual effect made from many tiny, short-lived pieces, such as sparks, dust, smoke, rain or confetti, each moving by simple rules. Together they suggest something too loose to draw as one shape. A small puff of particles when a character lands is one of the cheapest ways to add juice to a game.

See also Juice, Additive blending, Shader.

A way of saving progress without any memory in the cartridge: at the end of a stage the game shows a code of letters or numbers, and typing it in later puts you back where you were. The code quietly stores your level, items and sometimes score. Copying one down wrong was a familiar disappointment.

See also Save point, Cartridge, Cheat code. More in the Golden Arcade.

A fixed sequence of moves that reliably carries a player through part of a game, possible because many arcade games behave exactly the same way when given exactly the same inputs. Players shared patterns for the classic maze games, turning a seemingly unpredictable chase into something you could learn by heart.

See also Deterministic, Maze game, RNG.

Your own best score or fastest time on a game, kept separately from the public leaderboard. It gives every player a target to beat however they rank against others, and among speedrunners the abbreviation PB is the most common way of talking about a record run.

See also Leaderboard, Speedrun, Ghost (racing).

The coating on the inside of a cathode-ray tube screen that glows when the electron beam strikes it. Each spot fades over a fraction of a second, which gave vector games their soft trails and bright, slightly blooming lines. Colour screens use separate red, green and blue phosphors arranged in dots or stripes.

See also Cathode-ray tube, Vector display, Shadow mask. More in the CRT simulator.

The part of a game's code that simulates movement, gravity, collisions, bouncing and stacking, so objects behave like real things without each motion being animated by hand. Free 2D physics engines powered a wave of browser games where you fling, stack or balance objects and watch the consequences play out.

See also Gravity, Collision detection, Fixed timestep. More in the Flash Hall.

A coin-operated table game in which a steel ball rolls across a sloped, glass-covered playfield, and the player keeps it in play with flippers, aiming for bumpers, ramps and targets that score points. Its lights, chimes and score displays shaped how arcades looked and sounded long before video games arrived.

See also Coin-op, Arcade, High score.

The smallest dot of colour a screen can show, short for picture element. Every digital image is a grid of them. On old machines with low resolutions the pixels were large enough to see individually, so artists placed each one by hand and every dot had to earn its place.

See also Pixel art, Resolution, Bitmap. More in the Pixel Workshop.

Images drawn one pixel at a time, with each dot chosen deliberately, usually within a small palette and at a low resolution. It began as a necessity on early hardware and became a style of its own: many modern indie games choose big visible pixels on screens that could easily show photographs.

See also Pixel, Palette, Sprite. More in the Pixel Workshop.

A game where the main challenge is moving across platforms by running and jumping, judging gaps, heights and timing while avoiding hazards. The genre depends heavily on game feel: how a jump rises and falls, and small forgiveness tricks such as coyote time, decide whether it feels fair.

See also Coyote time, Jump buffering, Side-scroller.

An add-on program that extended what a web browser could do, such as playing animations, video or games inside a page. For years most browser games ran in plugins, which had to be installed separately. Security problems and the rise of HTML5 led browsers to drop them, and support for the best-known one ended in 2020.

See also Applet, HTML5, Preservation. More in the Early Web Hall.

A style of adventure game played mainly with the mouse: you point at things on screen and click to look at them, pick them up, talk to characters or use one object on another. It replaced the typed commands of text adventures, so players no longer had to guess the right words.

See also Text adventure, Mouse, Parser. More in the Early Web Hall.

A flat shape with straight edges, usually a triangle, used as the building block of 3D graphics. Every 3D model is a mesh of polygons. Early 3D hardware could draw relatively few of them in each frame, which is why characters of that era looked angular, and more polygons mean smoother curves.

See also Low poly, Wireframe, Shader. More in the 16-Bit Hall.

A version of a game moved from the machine it was made for onto a different one, such as an arcade game rebuilt for a home console. Early ports often had to cut colours, sounds or whole levels, because the home hardware had far less memory and power than the cabinet.

See also Remake, Console, Emulator.

A website that gathers hundreds of small browser games in one place, sorted into categories, with ratings and new arrivals on the front page. In the early web and Flash years, portals were how most people found free games, and many paid developers to show their logo inside a game.

See also Browser game, Preloader, Casual game. More in the Early Web Hall.

An item that gives the player a temporary or lasting boost when collected, such as extra speed, a shield or a wider paddle. Power-ups break up the rhythm of a game and reward taking a small risk, since the best ones often appear in awkward, hard-to-reach places.

See also Extra life, Score multiplier.

The small screen a browser game shows while the rest of its files download, usually a progress bar or a percentage counter. On slow connections it could sit there for a minute or more, so many Flash games filled the wait with a tiny playable toy or a sponsor's logo.

See also Portal (game website), Browser game. More in the Loading-bar wing.

The work of keeping old games playable and documented as the machines, discs and formats they need disappear. It includes copying ROMs before the chips fail, writing emulators, saving manuals and box art, and keeping browser games running after the plugins they relied on were switched off.

See also Emulator, ROM, Open source. More in the Flash Hall.

Making game content with rules and randomness instead of building every piece by hand, so the program creates levels, maps or items as the game runs. It lets a small team offer a world that is different on every visit, as long as the rules keep the results fair and playable.

See also Random seed, Roguelike, RNG.

Tricks that make a flat, two-dimensional picture look three-dimensional without the machine building a real 3D world. Racing games scaled roadside sprites up as they approached, and some consoles could rotate and stretch a whole background layer to fake a floor tilting away into the distance.

See also Parallax scrolling, Sprite, Racing game. More in the 16-Bit Hall.

A game where the main challenge is thinking rather than quick reflexes: sorting, matching, sliding or fitting pieces to reach a goal. Some are calm and allow all the time in the world, while others add a clock or falling pieces so that the planning has to happen under pressure.

See also Falling-block puzzle, Match-three, Daily challenge.

A game about reaching the finish line first or beating the clock, whether in cars, on bikes or in boats. Arcade racers often built a real steering wheel and pedals into the cabinet, and they drew the road with scaled sprites long before full 3D was possible.

See also Pseudo-3D, Time attack, Ghost (racing).

The starting number that a random number generator works from. The same seed always produces the same sequence of results, so two players given one seed get the same level or the same puzzle. That is how shared daily challenges stay fair, and Eracade's daily cabinet uses a shared seed.

See also RNG, Deterministic, Daily challenge. More in the Daily Puzzle Hall.

A way of drawing a picture as a grid of dots, built up row by row, which is how ordinary televisions and most screens work. Raster displays could fill shapes with solid colour, unlike vector displays, which only drew glowing lines between points on a dark screen.

See also Vector display, Scan line, Pixel. More in the CRT simulator.

A setting that cuts down on movement a game or website does not strictly need, such as screen shake, flashing, sliding transitions and spinning backgrounds. Some people feel dizzy or unwell from heavy motion, and modern devices let them ask every app to tone it down at once.

See also Screen shake, Colour-blind mode. More in the Daily Puzzle Hall.

How many times per second a screen redraws its picture, measured in hertz. Older televisions refreshed about 50 or 60 times a second depending on the country, and many retro games tied their speed to that rhythm, so the same game could run noticeably slower in one region than another.

See also Frame rate, Vertical blank, Cathode-ray tube.

A new game rebuilt from the ground up based on an older one, with fresh graphics, sound and code, and sometimes changed levels or controls. A remake keeps the idea and the spirit of the original, but it is a new piece of work rather than a polished copy.

See also Remaster, Port, Clone.

An older game updated rather than rebuilt: the original design, and often much of the original code, is kept while the graphics are sharpened, the sound cleaned up and the game made to run well on modern screens. It sits between a straight port and a full remake.

See also Remake, Port, Resolution.

A recording of a play session that can be watched back, or simply a reason to play a game again. Many games store replays as a list of button presses rather than video, which keeps the files tiny but only works if the game behaves exactly the same way every time.

See also Deterministic, Ghost (racing), Speedrun.

The number of pixels a screen or image has, written as width by height. Many early arcade and home games used resolutions of only a few hundred pixels across, which is why every pixel had to count and why their art looks chunky on a modern screen.

See also Pixel, Aspect ratio, Pixel art.

To come back into the game after losing a life, usually at a checkpoint, the start of the level or a safe spot nearby. Designers often add a second or two of flashing invincibility after a respawn, so the player is not caught by a hazard straight away.

See also Lives, Checkpoint, Continue.

A word for things from, or made to look like, an earlier era. For games it covers both genuinely old machines and new games that borrow their look and limits, such as pixel art, chiptune music and a handful of buttons. There is no fixed cut-off year.

See also Pixel art, Chiptune, Emulator.

A game where you press buttons, tap or move in time with music, and are scored on how accurately you hit each beat. The hardest part to build is the timing: designers have to allow for input lag and audio delay so that a perfect press actually feels perfect.

See also Input lag, Combo, Score multiplier.

Short for random number generator, the part of a program that produces unpredictable numbers for things like item drops, rival movements or shuffled pieces. Computers cannot easily produce true randomness, so most games use a formula that only looks random. Players also say RNG simply to mean luck.

See also Random seed, Procedural generation, Deterministic.

A game where each run takes place in freshly generated levels and everything is lost when the run ends, so the player starts again from scratch. The name comes from Rogue, an early dungeon game drawn entirely in text characters, and the style rewards understanding over memorising layouts.

See also Roguelite, Procedural generation, Turn-based.

A lighter cousin of the roguelike: runs still use fresh layouts and end for good when you lose, but some progress carries over, such as new characters, upgrades or shortcuts. That steady unlocking makes even a failed run feel useful, which suits short sessions on phones and in browsers.

See also Roguelike, Procedural generation, Power-up. More in the Indie Pocket Hall.

Read-only memory: a chip whose contents are fixed at the factory and cannot be changed by the machine using it. Arcade boards and cartridges stored their games on ROM chips, and today the word also means a copied file of that data, as used by emulators.

See also Cartridge, Emulator, Preservation.

The part of a screen where it is safe to put buttons, scores and text, away from edges a viewer might not see properly. Old televisions cropped their borders, and modern phones have rounded corners, camera notches and gesture bars, so games keep the important parts of the HUD well inside.

See also HUD, Touch screen, Aspect ratio. More in the Indie Pocket Hall.

A short recording of a real sound stored as digital data, such as a drum hit, a voice or a burst of applause, that a game can play back. Early machines had little memory to spare, so samples were kept brief and crunchy and mixed with synthesised chip sounds.

See also Sound chip, Tracker, Chiptune.

A fixed place in a game where progress can be stored, often marked by a glowing object, a book or a bed. Before games could save anywhere, save points let designers control pacing: a hard stretch felt tense precisely because the last save was a long way back.

See also Checkpoint, Password save, Continue.

One horizontal row of the picture drawn by a cathode-ray tube as its beam sweeps across the screen. On many old displays the thin dark gaps between rows were visible, and plenty of modern retro games add a scan-line filter to imitate that soft, striped look.

See also Cathode-ray tube, Raster, Interlace. More in the CRT simulator.

A number that every point is multiplied by while it is active, such as two times or five times. Multipliers usually grow with careful, unbroken play and reset after a mistake, which turns chasing a high score into a question of staying steady for as long as possible.

See also Combo, Chain, High score.

A quick jolt of the whole view that makes an impact, crash or heavy landing feel solid. Used in small doses it adds a lot of weight for very little work, but too much becomes tiring, which is why many games let players turn it down or switch it off.

See also Juice, Hit pause, Reduced motion. More in the Indie Pocket Hall.

A small program that runs on the graphics chip and decides the colour of each pixel or the position of each point in a scene. Shaders power lighting, water and glow effects, and retro-style games often use one to imitate the curve and scan lines of an old television.

See also WebGL, WebGPU, Scan line.

A thin metal sheet full of tiny holes that sits just behind the glass of a colour CRT, making sure each of the three electron beams only lands on its own red, green or blue phosphor dots. It is what gives many old televisions their fine, dotted texture up close.

See also Aperture grille, Phosphor, Cathode-ray tube. More in the CRT simulator.

Software that people could copy and pass on freely, usually with the first part of a game included and the rest available by paying the author. Shareware spread on floppy disks, magazine cover discs and bulletin boards, and it let small teams reach players without a shop or a publisher.

See also Bulletin board system, Indie game. More in the 16-Bit Hall.

A button on the top edge of a controller, pressed with the index finger while the thumbs stay on the front. Shoulder buttons gave players more actions without moving their hands, and they became standard on consoles from the 16-bit era onwards.

See also Gamepad, D-pad, Analogue stick. More in the 16-Bit Hall.

A game viewed from the side in which the screen moves left or right to follow the player through a level. Most classic platformers work this way, and many add parallax scrolling, with distant layers moving more slowly than near ones, to make a flat scene feel deep.

See also Platformer, Parallax scrolling, Top-down view.

A game in which the player steers a line around the screen, collecting food that makes it longer, and the run ends if the head touches a wall or the growing tail. It became familiar to millions on early mobile phones, and its rules are simple enough to make it a common first project for new programmers.

See also Maze game, Game loop, Endless runner.

A chip dedicated to making sound, so the main processor can get on with running the game. Early sound chips offered a few channels of simple waveforms plus noise, and the particular character of each chip is a big part of why music from different machines sounds so distinct.

See also Channel (sound), Chiptune, FM synthesis. More in the Chip Synth.

An attempt to finish a game, or part of one, as fast as possible, usually timed and recorded so others can check it. Speedrunners study games in great detail, finding shortcuts, routes and sometimes glitches, and they agree on categories so that runs can be compared fairly.

See also Time attack, Glitch, Personal best.

A knob controller that turns freely in either direction, letting the player move something quickly and precisely across the screen. Spinners suit games about steering or aiming around a circle, because the speed of the turn matters as much as its direction, which a joystick cannot capture.

See also Paddle controller, Trackball, Control panel. More in the Vector Hall.

A small image that moves around independently of the background, such as a character, a ball or a falling piece. Many older machines had special hardware for drawing sprites on top of the scene, which kept movement smooth but limited how many could appear at once.

See also Sprite flicker, Tile map, Pixel art. More in the Golden Arcade.

A blinking effect seen when a game wants to show more sprites than the hardware can draw on one line or in one frame. Rather than let some vanish completely, the game takes turns drawing them on alternate frames, so each one is visible part of the time and appears to flicker.

See also Sprite, Frame, Scan line.

A sound wave that flips sharply between two levels, giving a bright, buzzy tone. It is one of the easiest waveforms for simple hardware to make, so many early sound chips relied on square-wave channels for melodies. Changing the width of each pulse changes the colour of the sound.

See also Triangle wave, Noise channel, Sound chip. More in the Chip Synth.

An animation idea borrowed from cartoons: objects flatten when they land or bump into something and lengthen when they move fast or leap. It makes things look soft and full of energy, and in games even a few frames of it can make a jump feel springier.

See also Juice, Easing, Game feel. More in the Indie Pocket Hall.

A game told entirely in words, where the computer describes a place and the player types short commands such as go north or take lamp. A parser reads the commands, and the fun lies in exploring, solving puzzles and working out which words the game understands.

See also Parser, Point-and-click. More in the Revived Wing.

A small square of graphics, often 8 or 16 pixels on a side, that is reused many times to build a background or level. Storing one tile and repeating it saved a great deal of memory, which is why older game worlds are made of clear, repeating blocks.

See also Tile map, Sprite, Pixel art.

A grid that records which tile goes in each square of a level or background. Instead of storing a whole picture, the game keeps a short set of tiles and the map that arranges them, which makes large worlds cheap to store and easy for designers to edit.

See also Tile, Level editor, Sprite. More in the Golden Arcade.

A mode where the goal is to finish a course, level or task in the shortest possible time, rather than simply to finish it. Times are usually saved to a table so players can chase their own records, and many games let them race against a ghost of their best attempt.

See also Speedrun, Ghost (racing), Personal best.

A camera angle that looks straight down on the game world, or nearly so, like a map. It makes it easy to see everything around the player at once, which is why it suits maze games, racing on twisting tracks and many early adventure games.

See also Isometric view, Side-scroller, Maze game.

A display that senses where fingers touch it, so the screen is also the controller. Games for touch screens tend to use taps, swipes and drags rather than many buttons, and designers have to stop the player's fingers from covering the very action they need to see.

See also One-button game, Haptics, Safe area. More in the One-Tap Hall.

A strategy game where rivals march along a path and the player places towers beside it to stop them reaching the end. The puzzle is choosing what to build and where with limited resources, and the genre grew especially popular as free browser games on the early web.

See also Wave (of enemies), Browser game, Turn-based. More in the Early Web Hall.

A controller built around a large ball set into the panel, which the player rolls with the palm to move a cursor or character. It gives fast, smooth movement in any direction, and a hard spin keeps the ball rolling, so it suits games about rolling, aiming or sweeping across the screen.

See also Spinner, Mouse, Control panel.

A music program that arranges notes in vertical columns, one per channel, scrolling down the screen as the song plays. Trackers made it possible to compose with short samples on home computers, and they are still used to make chiptune and demoscene music today.

See also Sample, Chiptune, Demoscene.

A sound wave that ramps smoothly up and down, giving a softer, rounder tone than a square wave. On some early consoles a triangle channel handled bass lines and gentle melodies, because its mellow sound sat neatly underneath the brighter square channels.

See also Square wave, Noise channel, Channel (sound). More in the Chip Synth.

Describes a game where players take turns to act, rather than everything happening at once in real time. Nothing moves until a decision is made, so there is time to plan, which makes turn-based design popular for strategy games, puzzles, card games and roguelikes.

See also Roguelike, Auto-battler, Puzzle game.

The part of a game that teaches the controls and rules, often through the first level rather than a page of text. The best tutorials are almost invisible: they set up a safe situation in which the player discovers a new move simply by trying it.

See also Difficulty curve, Attract mode, Level (stage).

A game or program printed as a listing in a magazine or book, which readers typed into their home computer line by line. It could take hours, and a single typing mistake might stop it running, but many people learned to program by working out what each line did.

See also Home computer, Bug, Homebrew.

The standard tall arcade machine that players stand in front of, with the screen at eye level, the controls on a ledge below and a lit marquee on top. Its narrow footprint let arcades fit many machines side by side along their walls.

See also Arcade cabinet, Cocktail cabinet, Marquee. More in the Golden Arcade.

A screen that draws images as bright lines between points, steering the beam directly instead of sweeping across rows like a television. The lines were sharp and glowing but could not easily fill shapes with colour, which gave vector games their distinctive outlined look on a black background.

See also Raster, Wireframe, Phosphor. More in the Vector Hall.

The short pause after a screen finishes drawing one picture, while the beam of an old television returns from the bottom to the top. Games used this gap to update their graphics safely, because changing them halfway through drawing could cause tearing or flicker.

See also Refresh rate, Frame buffer, Scan line.

The four letter keys W, A, S and D, used on a computer keyboard as arrow keys for the left hand. The layout leaves the right hand free for the mouse and keeps many nearby keys within reach for other actions, which is why it became the default for computer games.

See also Key binding, Mouse, D-pad.

A group of rivals or obstacles that arrives together, followed by a short breather before the next group. Waves give a game a clear rhythm of pressure and rest, and each new wave is usually a little faster, larger or trickier than the one before.

See also Tower defence, Difficulty curve, Pattern (arcade).

A compact, fast format for code that runs inside web browsers alongside JavaScript. It lets programs written in languages such as C, C++ or Rust run in a web page at close to native speed, which made it practical to bring full game engines and emulators to the browser.

See also HTML5, Emulator, WebGL. More in the Indie Pocket Hall.

A way for web pages to use the computer's graphics chip to draw 2D and 3D scenes quickly, without any plugin. It is based on OpenGL ES, a graphics standard used on phones and other small devices, and it helped smooth browser games carry on after Flash faded.

See also Canvas, Shader, WebGPU.

A newer web standard that gives browser pages more direct, modern access to the graphics chip than WebGL. Besides drawing, it can use the chip for general number-crunching, which helps with large particle effects, physics and other heavy work inside the browser.

See also WebGL, Shader, WebAssembly. More in the Daily Puzzle Hall.

A way of drawing 3D objects as only their edges, like a frame of wire with no solid surfaces. It needed far less computing power than filled shapes, so many early 3D games, especially on vector displays, showed worlds made entirely of glowing outlines.

See also Vector display, Polygon, Low poly. More in the Vector Hall.