Pretty good, but my god you need some UI work. Hotkey to switch between units and spells or better yet, put spells as buttons on screen so you can see when they are ready. Button for placing castle waypoint. When a game is this fast, UI is key. Look at how many keyboard shortcuts an RTS has.
In the sixth mission, I only got hit once and passed it easy, but it said I left 4 behind. Is it because I killed all the aliens before pressing the buttons when the mission briefing said to do it the other way around?
I totally loved this game when it came out! Kinda looking forward to replaying to get all the cards again. But, and I can't believe I'm saying this, SPARK IS STILL BROKEN.
This game continues to be awesome. But don't put an undo button. Even when games have a "can't undo if you discover something" feature, the fact you can undo there shows you that there is nothing in that direction.
You still collide with popped balloons. And don't dealloc the doors. THe game hitches every time you land so they can load. Just send them to the back.
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Your troopers need to be on the same side of the doors Beckett and Pierce are, if not, they are stranded with the aliens.