Hey, thanks for playing and commenting and stuff! It means a lot :)
As noted in the hints, the cost of a turret is 200 energy. So if you place a ton of turrets, you'll die haha. I meant to show the cost of a turret with the icon in the lower left corner but ran out of time. Perhaps the cost of turrets should've been 500 or something, which probably would've been more noticeable to the player.