The rules of the game are very simple. You score the points by breaking up blocks of rubble. Breaking up a block causes the blocks which were supported by it to fall down (due to gravity, of course). When Kret is crushed, the game is over. He hasn't got another life!
You only need three cursor keys to control the game - 'left', 'right' and 'up'. If you need to move the animal down, just place it above some empty space and wait. Kret will fall down on his own! Note that Kret flaps his paws. Because of this he falls down twice slower than the blocks, which is why they may catch up with him and crush him! What follows is that you need to make sure that the space over Kret's head is empty.
As soon as you break up a certain number of blocks, the level is automatically raised and the game speeds up. Kret's slow movements get brisker and the game becomes more difficult.
Breaking up blocks pose another difficulty. From time to time a randomly chosen block breaks up. Note that this only happens to the bottom blocks - those resting directly on the floor of the dungeon. With time they are going to prove the greatest threat to Kret's life.