The bubble graphic looks really nice.  I think that the difficulty maybe didn't scale up enough as it never really became challenging (I finally let the enemies kill me after a few minutes).  A score, maybe some bigger enemies that need prolonged contact with the shield, some variety here would have helped possibly.  The code appears to work very efficiently--I never experienced any lag or performance issues.  A button for ending the game would be beneficial as I had to ctrl+alt+delete out, but that's okay for a jam.  Overall really good work.

Cool idea! one problem is I don't think there is anything stopping you from just spamming Q and E to survive forever. Maybe you could restrict how often the player can switch colors and have some sort of recharge bar, this would force the player to make their button presses count.