Really fun, but I do have a couple gripes:
- There has to be a bit more of a "buffer period" when the upgrades come up because too often I'll be firing away and accidentally place down an upgrade I didn't want
- The player's attack speed starting out is really sluggish without upgrades (and still is even with them). The enemy heath and density is definitely enough to keep a base firing boost speed in check
- The way you place down upgrades is cool and could definitely open up some base builder-esque strategies, but they do make piercing miserable to use (maybe have them not take damage from projectiles that have already pierced enemies?)
- As much as I love it, the multi projectile upgrade makes damage obsolete. Damage as a whole just needs a buff, since one upgrade level doesn't make it easier to kill either of the most common enemies
Don't get me wrong: This game is still really fun and has some cool upgrades (like the bullets just hanging there after hitting something). Honestly, most of this critical feedback was specifically because this concept is worth revisiting.