After completing Level 25, you will unlock the Depressor Beam, which squashes things. Level 26 gives you a stone to drop in a hole. Do so, activate it with your Depressor beam and trace the patterns in the grass with your Beam. Repeat for the other hole. Make sure you're very precise, don't over do it and only squash when the grass is highlighted thanks to the stone. You must then complete the quota in the level for both to count. There are a total of 10 in the game: 5 in Singleplayer and 5 in Multiplayer.