Store

Went through a few iterations of how to add level spikes in, ended up on a store.

Started with a currency... but collecting minions is already a thing, and if I keep this project going long a "meta" currency like most suvivor games have is probably inevitable.  So I think spending mininions in exchange for benefits feels like a good compromise.

Also added is a tower builder that periodically takes away minions to build towers.  Early game it definitely feels week, but starts to ramp up well.

My time to defeat the boss w/ +5 minions was 72 seconds, and w/ tower builder 79.  It felt like I was gathering a lot more stuff 30 seconds later though with the towers.  Which statwise they almost double the dps, and I think the benefit of a separate bullet point yields more bullets hitting on the long term.

Final thought, I didn't mention this before but the enemy spawner I ended up with is based on the total "threat" (arbitrary points I assign to an enemy) on screen.   It increases at 1 per second & starts at 10.  The effect this ends up having is the better you are killing enemies in the current wave, the more that spawn.  So this rewards aggressive play by letting you accrue minions faster,  vs punishing you with gaps in time.