Version 0.43 is out, and includes a range of fixes and features:
Enemy rendering / performance fix - one draw call for all, instead of one draw call each
Enemy selection / performance fix - speed up for when towers are selecting an enemy to shoot at
Upgrade screen UI update
Main menu UI update, including an animation on the RHS
Enemies get a speed boost if more than 5 waves are active
Enemies will wait longer before rerouting
Reduce the number of times a wall has be broken before the tile it's on cracks
Bugfix: Game froze if clicking the settings menu while editing a tower
Bugfix: Clicking a gem in the hotbar for a second time should deselects it
Bugfix: Tabs fixes - it now selects the next tetromino correctly, and doesn't cancel fast forwarding
I've also updated the screenshots and trailer.