alpha 0.9 is out! It has lots of big changes to a run's flow, some fun new fellas to meet and shoot, and local co-op. I'll go into the details now!
New Minibosses

DEATH STARFISH

SUNBEAM: I really like how this goofball's weird attack works and how you can match-3 to get past its armor.
Upgrade Rocket, Item Shop

No more level-up interruptions! Level up all at once after minibosses/bosses, and spend your coins on items! For now, all items are heals. I'd like to add a variety of things in the future. This really changes the flow and pace of the game for the better, but it certainly changes a level's difficulty curve. I hope that the extra boss rewards provided by scouts will help that.
Scouts, better level pacing

These fellas only show up once you buy the "Scouts" upgrade in the Ichor Upgrades Shop! They'll let you pick which boss to fight and which rewards to get. For now the rewards are kinda big and simple: piles of coin or XP. I don't think they make things too easy, given the somewhat delayed upgrade path.
This is part of an overall goal to better pace the levels and give you more control over your run in this update. The game will now spawn waves sooner and scroll levels faster if the screen is cleared of enemies and obstacles, too!
Local co-op

Right now this is a carry-your-friends (i.e. kids) mode. It's a lot of fun as is, but I'm open to a more traditional/tough co-op mode where there's a shared health pool, etc. I'm eager to hear your feedback on this and hope you enjoy it!

I also added a tutorial for where the player's weak point is! Sorry I didn't do that earlier, although I imagine a good few of you figured it out already. It's the pupil.
Here are the full patch notes. It's a lot!
alpha 0.9 Patch Notes
Added upgrade shops. No more level up interruptions!
Level up after minibosses and bosses, spend coins on items.
Added Scouts ichor upgrade: pick which boss you'll fight, and rewards!
Added local co-op! It's a carry-your-friends mode.
Tell me if you want a harder co-op experience, too!
Added miniboss: DEATH STARFISH
Added miniboss: SUNBEAM
Added coin, unspent level-ups to player HUD.
Added weak point tutorial to in-game tutorial and how to play menu.
Improved level pacing:
tighter wave spawning if the screen is cleared early.
levels 2 and 3 now scroll faster if the screen is clear.
Fixed held fire button resulting in instant upgrade acceptance if fire/confirm are bound to the same key
Fixed zapper network enemies on level 3: more variable formations, more of them.