The lessons

Taking a game apart tells us what it does. A lesson is the other half: a small cartridge of our own that does the same thing, written from what we measured and measured again the same way, so the two can be set side by side. Its program is ours, so it is shown whole, and the cartridge is yours to play.

How a character moves: jumping, running, landing on things, being carried by them, bumping into them, and the box that decides a touch

• A jump that feels like Mario's: A cartridge of our own whose square walks and jumps with the numbers read off Super Mario Bros., measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• Running, and why a running jump goes higher: A cartridge of our own where B makes the square run, and the jump it takes depends on how fast it was going, with the speeds and pulls read off Super Mario Bros., measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• A stomp and a hit, told apart the way Mario does: A cartridge of our own where touching a walker from above, falling, flattens it and bounces, and any other touch is a hit, the way Super Mario Bros. was measured telling them apart, measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer, Where two things are compared.
• A box inside the picture, the way Mario's is: A cartridge of our own where the square and a walker each carry a box smaller than their pictures, kept in memory every frame with the sizes read off Super Mario Bros., and only the boxes decide a touch; Select shows them. Measured beside the game, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer, Where two things are compared.
• Ground, a block and a wall, solid the way Mario's are: A cartridge of our own whose square looks the level up at its own edges: it stands on the ground, bumps a block from below and stops at a wall, compared by that shape with how Super Mario Bros. was seen doing it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• A moving platform that carries you, the way Mario's lifts do: A cartridge of our own where a lift goes back and forth over a hole, and the square standing on it is moved by the lift's own step on the same frame, with nothing pressed, compared by that shape with how Super Mario Bros. was seen carrying Mario on its lifts, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, Where two things are compared.
• A coin from a block and the score, the way Mario's are: A cartridge of our own where bumping a block pops out a coin that turns as it rises and falls, counts the coin and the points into a bar at the top on that frame, and floats the points up after, compared by that shape with how Super Mario Bros. was seen doing it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• Walkers that turn at walls and at each other, the way Mario's Goombas do: A cartridge of our own with two walkers that go a pixel every second frame, turn around when they walk into a wall, and both turn when they meet, compared by that shape with how Super Mario Bros. was seen moving its Goombas, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, Where two things are compared.

How the picture is made: scrolling, the camera's dead zone, rooms, screens, a bar that stays and sprites that flicker

• A picture that scrolls the way Mario's does: A cartridge of our own whose picture follows the square and builds the land ahead in strips, the way Super Mario Bros. was measured doing it, measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• The camera's dead zone, the way Mario's is: A cartridge of our own where the camera lets the square walk a stretch of the screen without following, eases in past 80 pixels and holds it at 112 walking right, as Super Mario Bros. was measured doing, and, unlike the game, follows it back walking left, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• Rooms that slide in the way Zelda's do: A cartridge of our own that holds the picture still and brings the next room in when the square walks out of one, sliding across and writing over itself up and down, the way The Legend of Zelda was measured doing it, measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• One byte chooses the screen, the way Mario's does: A cartridge of our own with a title, play and a pause chosen by one byte through a jump table after a call, the way Super Mario Bros. was measured choosing its screens, and what our own autopsy says of it. Our own autopsy, run over it, names: The poll, The wait for the frame, The jump engine, The picture writer, The palette writers, The sprite writers, The scroll writer.
• A status bar that stays still, the way Mario's does: A cartridge of our own whose level scrolls under a bar that does not move, split where sprite 0 meets the bar's bottom line, with a timer written only when it changes, the way Super Mario Bros. was measured doing it, measured beside it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer, The split.
• Too many sprites on a line flicker rather than vanish, the way Mario's do: A cartridge of our own with ten figures on one line, two more than the console draws, where Select turns the order they are written in from frame to frame, the way Super Mario Bros. was seen moving its sprites about, so that no figure is always the one left out, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers.

The screens around the game: splash, title, menu, pause, items, the story, a life lost, a hole fallen into, a level's end, and the end

• A splash screen that moves without drawing, the way Zelda's does: A cartridge of our own whose splash screen writes not one tile while it shows: drops of water that are sprites falling in a loop, a word whose colours turn by rewriting the palette, and a fade to black by palette, compared by that shape with how The Legend of Zelda's title was seen doing it, with its program. Our own autopsy, run over it, names: The wait for the frame, The picture writer, The palette writers, The sprite writers.
• A title drawn into the level, the way Mario's is: A cartridge of our own whose title is written into its level's picture, with a menu whose cursor is three background tiles and a countdown into a demo that scrolls the title away, compared by that shape with how Super Mario Bros. was seen doing it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• A name typed from a grid, the way Zelda's is: A cartridge of our own for typing a name: a grid of our letters, a blinking cursor drawn behind them that moves the frame after a press, repeats when held and carries on round the grid, and A writing one letter into the name, compared by that shape with how The Legend of Zelda was seen doing it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The sound driver.
• A pause that holds the world still, the way Mario's does: A cartridge of our own whose Start button pauses it: the square holds, nothing is drawn, the tune is cut for a chime of our own, and Start is ignored for a while, compared by that shape with how Super Mario Bros. was seen pausing, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer, The sound driver.
• Losing a life and starting again, the way Mario does: A cartridge of our own where touching a walker ends the round: everything holds while the square hangs, it hops and falls off the screen, a screen says how many lives are left, and the level begins again from its start, compared by that shape with how Super Mario Bros. was seen losing a life, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, Where two things are compared.
• The level's end, the way Mario's is: A cartridge of our own where touching the pole at the end of the level hands the game to itself: the pad is ignored, the square slides down and walks to the door by itself, the time left is counted into the score, a card names the next level, and the next level begins, compared by that shape with how Super Mario Bros. was seen ending a level, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers.
• Falling into a hole, the way Mario does: A cartridge of our own where walking off the edge of a hole drops the square through the bottom of the screen, steering still working on the way down and the walkers still walking, until a wait runs out, the life is taken and the level begins again from its start, compared by that shape with how Super Mario Bros. was seen falling into a hole, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, Where two things are compared.
• The last life, and what comes after it, the way Mario does: A cartridge of our own with three lives to lose: the last touch goes straight to a GAME OVER screen that holds by itself, then to a title that waits for Start, and Start begins the game again with its lives back, compared by that shape with how Super Mario Bros. was seen ending and starting over, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, Where two things are compared.
• An item screen the picture slides away to show, the way Zelda's does: A cartridge of our own whose Start button slides the whole picture down to show an item screen above it, drawn a row at a time just ahead of the slide, compared by that shape with how The Legend of Zelda was seen doing it, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.
• Words that crawl up the screen, the way Zelda's story does: A cartridge of our own whose about screen crawls our own words up the screen a pixel every second frame, writing one row each time the words have moved up a row, through both stacked screens and round again, compared by that shape with how The Legend of Zelda tells its story, with its program. Our own autopsy, run over it, names: The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer.

Sound: two sounds on one channel

• A jump sound that borrows the music's channel, the way Mario's does: A cartridge of our own with a tune and a jump sound, both ours, sharing one square channel the way Super Mario Bros. was seen sharing it, compared by that shape only, with its program. Our own autopsy, run over it, names: The poll, The wait for the frame, The picture writer, The palette writers, The sprite writers, The scroll writer, The sound driver.