Tap a cannon in Up Next or Waiting to send it onto the belt. Up Next is the front of five queues, each with a slot below it showing what spending that queue brings up, and a count of how much of it is still out of sight. Waiting is what came home still loaded.

Passing a row or column, a cannon fires only if the nearest pixel is its own color. Anything else and it holds fire, so peel the picture from the outside in.

A cannon that empties is done. One that comes home still loaded takes a waiting slot, and sending it out again is up to you — unless there is nothing left to send in its place, in which case it stays on the belt and keeps going round.

There are only five waiting slots. Fill all five and the next cannon home has nowhere to go, the belt locks, and the run is over. Never send more at a color than the picture still has of it.