Players try to reach the highest point on the ever changing board. In a turn, players either place a tile, place their pawn on the board, or move their pawn if it's already on the board.
Moving a pawn is allowed under the condition that for each step (based on the square grid of the board), the pawn has to either go up or down one level. Precisely one level. Too steep a climb or descent and the pawn can't go there. Movement on the same level is also not allowed.
The players that reaches the highest point is the winner. In case of a tie, the player that is on the largest plateau wins. If this doesn't solve the tie, then the player that has been on the highest point the longest is the winner.
With two players, the game is very strategic. With 3 or 4 players luck also becomes a factor to take into account.
EDIT (November, 2nd 2011): There's a new supplementary rule (approved of by Winning Moves):
Players are allowed to remove their own pawn from the board as a separate move (and re-enter it on the ground level at some later point of the game as a separate move).