Paint Slide

Goal

A ball of paint slides across a gridded canvas. It sets off in the direction you choose and only stops when it hits a wall or a block. Every square it crosses gets coloured. Colour all the free squares of the canvas in as few moves as possible.

How it works

• Swipe the screen, drag the mouse, click or tap on the side of the ball you want it to go, or use the keyboard arrows (or W, A, S, D).
• The ball does not stop by itself: it runs until the first obstacle.
• A square that is already coloured stays coloured: crossing it costs nothing, but gains nothing either.
• Each slide counts as one move. The best known route is worked out by a solver, and your stars depend on the gap with it: three stars if you match it.
• If the canvas can no longer be fully coloured (a dead end), a red frame tells you: undo some moves or start over.

Canvas elements

• Walls: wooden boards that stop the ball, like the edge of the canvas.
• Portals: a ball that enters a portal comes out of its twin, of the same colour, and carries on in the same direction. Both squares get coloured.
• Icy squares: the ball crosses them without colouring them. To paint one, you have to stop on it.
• Paint pot: a movable pot that the ball pushes one square. If it is against a wall or another obstacle, it blocks the ball. The square it covers at the end does not need to be coloured.

Levels

• Easy: 5 × 5 to 6 × 6, a few walls.
• Medium: 7 × 7 to 8 × 8.
• Hard: 9 × 9 to 10 × 10, with portals.
• Expert: 11 × 11 to 12 × 12, portals and ice.
• Devilish: 13 × 13 to 15 × 15, portals, ice and a paint pot.

Each level has its own paint colour, and every canvas is drawn at random. The solver checks that every maze can be completed.

Game modes

• Solo: moves, stars, hint, undo and a visible autopilot. Records are only registered without hints or autopilot.
• Against the AI: the Paint AI colours a miniature copy of the same canvas at its own pace. The first to finish wins. No hints and no undo.
• Two players: on the same device, same canvas, one after the other. The fewest moves wins, then the time in case of a tie. The moves of a fresh start stay counted.
• Online: a simultaneous race on the same canvas. The fewest moves wins, then the time.

About the AI

The solver explores the slides by iterative deepening: it looks for the shortest route that colours the whole canvas, pruning the branches where the number of squares left exceeds what the remaining moves could ever cover, and remembering positions it has already seen. This same solver provides the goal in moves, the hints, the dead-end detection and the autopilot. The Paint AI follows a route computed by it, more or less carefully and more or less quickly depending on its level: Careful, Skilled or Virtuoso.