This a really lovely concept. The rush of quickly throwing together defences before the spiders got out of control was ace. Two main points of feedback (Which I totally understand why isn't possible in the time constraints):
1. Energy replenishing should be significantly slower or non existent to force the player to rely on the energy cubes more. Once I'd blocked off all the exits, I didn't have a reason to interact with the blocks again (Other than sometimes using them as cover!)
2. Enemy pathfinding - Obviously a tough nut to crack, but having the enemies actively swarm entrances with no blockades would be nice.
I genuinely think there's potential with this project for more depth - Having things like a day/night cycle which involves using energy on lighting and a shelf life to the energy cubes would be great (Possibly re-charge points?)
Music was catchy as heck, btw.