Pretty simple, but surprisingly fun! You could probably do some things to improve it a little.
There should be some indication that your character is ready to strike. Like a sound cue, or maybe he could hold a weapon he crafted.
Bosses could have several hit points. Like after collecting all the stuff and atacking, you could do that again, but now the boss moves faster.
I couldn't pass the level with a tree. I collected four objects, but I can't attack the virus. Is he a giant virus? If so- cool idea!
One more thing, but that's just my personal taste. Controls would be better if space was jump and shift dash.