Enjoyed thius for a while but got really repetative.
Ended up with mostly crushers and one or 2 guns.did't find a way to sell structures I don't want anymore.
Would be more interesting if there wehre more enemy types, like flying enemy, "hard hat" enemy that can stop a crusherand so on.
Same goes for structures - more variety would be cool.
I'd also say repairing structures is annying - would be geeat if they self repaierdeither at start of the wave or periodically.