Slime Glutton

You are a slime. You cannot attack. All you can do is touch things and swallow them. A mob smaller than you can be swallowed. Touch a bigger one and it swallows you instead, and the run is over. The same mob is food or a threat depending on your size. Swallow 500 to clear. The bigger you get, the heavier you move. Dig up chests along the way and fill the gem collection.