Very interesting take on the theme! The mechanic of having to shoot circles inside other circles to deal more damage to the slowly growing and approaching enemy makes for really interesting movement! For feedback, I did lose the smaller circles and couldn't shrink the enemy, so I'd suggest scattering a number of smaller circles around the arena, or having an arrow point to the small circle. Also, having the lack of energy or whatever it was called only making the enemy grow faster but not slowing or stopping your shooting speed makes it sort of unclear.  This isn't to say that these are things that SHOULD HAVE already been considered before the game was submitted (there was only like 4 days lmao), just wanted to share some of the thoughts I had while playing your game! Sorry for typing too much, I'll stop now!