Snake

• The snake moves one cell forward every tick, on its own, whether or not you touch anything.
• You may turn left, right or carry straight on. The direction opposite your heading is refused, never obeyed.
• Eating the apple adds one cell to the tail and puts a new apple on a cell the snake is not occupying.
• Leaving the board ends the run. There is no wrap-around here — the four edges are walls.
• Touching your own body ends the run, with one exception: the cell your tail is leaving this tick is already empty, so following your own tail is legal.
• Filling every cell on the board is a win. There is nowhere left to put an apple, and that is the end of the game rather than a crash.

Because a turn is usually written straight into the snake's heading, and a second press inside the same tick overwrites the first. At the Steady clock a tick is 120 milliseconds and at Blitz it is 60; any two presses closer together than that land inside one tick. Take a corner with up-then-left and the snake goes only left, into the thing you were steering round.

Here a turn is put in a queue two deep and the clock takes one entry per tick. Press up then left inside a single tick and the snake goes up, then left: both corners, in the order you asked for them. Two is deliberate — a queue three or four deep starts executing a plan you have stopped watching, and a press that arrives with the queue already full is refused rather than allowed to displace one you have already committed to.

Yes, and the win is not theoretical. Every board here has an even number of rows, and an even grid always contains a closed tour that visits each cell exactly once. A snake that simply follows that tour can never meet itself, because its body is always a run of consecutive cells along the tour — so it eats every apple in turn and ends up as long as the board. On the 12 × 12 board that takes fewer than 6,000 ticks, which is about twelve minutes at the Steady clock.

Following the tour is a proof, not advice: it is also the slowest possible way to play, since it walks the whole board between apples. Real play cuts corners, and the moment you cut one you can trap yourself. That gap between what is provably possible and what is actually survivable is the entire game.

An apple is worth the length of the snake that swallowed it. The first is worth 4 points, because the snake starts 3 long and the apple makes it 4; the last one on the 20 × 20 board — the 397th, which fills the four-hundredth cell — is worth 400. That is the whole scoring rule, and it prices the game honestly: the last apple on a crowded board is the hard one, and a flat ten points each would rate it exactly like the first.

Because the score follows from the length alone, it is also tamper-evident: a saved game whose score and snake disagree is thrown away rather than restored, so a hand-edited file cannot write a record into the statistics panel. The speed you choose is kept out of the score entirely, which is what makes a best score on a board comparable however fast you set the clock.

Not here. Plenty of versions shorten the interval as the snake grows, which sounds like rising tension and plays like a countdown: the player who is doing best is punished hardest, and every game ends at roughly the same wall-clock moment whatever they do. The tick you pick at the start is the tick on the last apple.

The snake also starts a third of the way across the board rather than in the middle of it, which gives seven cells of runway on the 12 × 12 board before the right-hand wall instead of five. At the Blitz clock five cells is 300 milliseconds to make a first decision, which is not a decision. The clock does not start at all until your first turn.

On one of the free cells, chosen with a single draw over the list of them — never by picking a random square and trying again if the snake is on it. On an almost-full board that retry loop is a disaster: with one cell free in four hundred it expects four hundred attempts and has no upper bound at all, so the game stutters exactly when it matters most. Drawing from the free list costs the same at every length, and it makes the endgame honest, because a board with no free cells is a win rather than an infinite loop.

Every draw is a pure function of the game number and the count of apples already eaten, so game #914 plays out identically on every device: the same opening board, and then the same apple after the same moves, forever, with nothing stored on a server. Where the apple lands does depend on your snake — it is drawn from the cells you are not standing on — which is why two people on game #914 who have played differently can see the same draw land in different places. The first 30,000 game numbers open on 30,000 different runs, so the number on the status bar is a real identity and not decoration — replay it from the end card and the board comes back exactly as it was dealt.