No opponent — just sealed cards, a shuffled board, and three chances to fix a mistake.
A handful of cells start sealed with cards you don't control. Their positions are shuffled every puzzle, but each one always has at least one open cell touching it, so it's never impossible to flip. The rest of the cells are empty.
Place your hand cards into the empty cells. When you place a card, compare its touching number against every adjacent card — sealed or already yours — and if yours is higher, that card flips. Flipping just swaps its color, so a card you already own can be flipped back to sealed by a later placement.
You win the instant every card left on the board is green — you don't need to place your whole hand, and any cards still in hand once that happens just don't matter.
Tap a card, then tap an empty cell to place it. You can pick a placed card back up to reposition it, but only 3 times per attempt — after that, every placement is final. Dimmed numbers face the edge of the board and never touch anything.