Fun little game. Just as I thought it was a little too easy the intensity increased.
There didn't seem to be anything preventing you from stacking different puddles on top of each other? If they replaced each other or even mixed to become a different color it would prevent you from camping in the same location.
I went ahead and made two changes per your your notes. I've added ammo pickups to motivate player movement. I've also added "hard mode" (on by default) which creates the effect that overlapping potions of different colors are immediately neutralized and will not hurt enemies.
I think you're right that this gets the player moving and makes for a more exciting game. You have great design instincts!
If these notes affected your rating of the game, re-evaluation is greatly appreciated :)
