Mordant is flood-fill: a stain starts in the top-left corner. Pick a colour and the stain repaints — any board cells of that colour touching the stain join it too. Keep choosing colours until the stain covers the whole board, before you run out of moves.
Clear a round to open the next one, with one move fewer than before.
Clearing a round earns points equal to the moves you had left — double in Daily. Spend them in Endless to continue a lost run with 3 extra moves.
Choose a mode
Round after round, a new board each time — one move fewer every round, until you run out.
One board a day, the same for everyone. One attempt — come back tomorrow for a new one.
Round after round, a new board each time — one move fewer and three seconds less every round, until either runs out.