Is there a solution to -2 (The Power of Cheerfulness)?
If anyone else wants to see: get at least 5 lives, then go to level 1 and feed them to the plant.
Grab the extra life in -1, kill all the enemies, have the music off, and die on the spikes until you'd game over; it'll transport you to -2 on your last death.
From there, I have no clue what to do.
Edit: To clarify, you can grind lives by cycling through the levels (earn points, replace the level with a point value, pick up any lives you find around; you'll eventually get to 5. Keep in mind resets lower score by 1.)
Edit II: To beat -2, get to the end of the level without harming an enemy. This was very obscure.
If the dev sees this: I see what you meant by "cheerfulness" and the enemies smiling, but it's a bit of a logical leap. Something like "the power of pacifism" or "the power of little snowman dudes" could be a bit clearer. As it is now, I tried things like jumping in place a bunch, making the enemies dance around, etc. as I didn't have anything to go on. I would have given up if I hadn't happened to try pacifism.
You are the creator: do with what I said however you want to. I'm just telling my experience.
edit III: soft lock on -4, aaaaand I give up. too tedious and I ceased to care