RXP is Rock Scissors Paper on a board.

Rock beats Scissors, Scissors beat Paper and Paper beats Rock.

When you beat Rock from the board, you remove it from the board and you get rock, you can then use Rock to beat scissors on the board and so on until you clear the complete board.

But attention: the symbol you beat next must be on a square that neighbours the previously beaten symbol (diagonal neighbours don't count). Too complicated? Complete the initial tutorial levels and learn by playing.

You beat a level if you manage to clear the board. Think strategically before you make your move because otherwise you might get stuck with no way to clear the board.