I love coop games so it was cool to see one in a jam since people don't normally make them for various reasons. I also really like tower defense games and I thought it was a good application of the theme. Damaging in between waves so you have to maintain your defense is really fitting for a tower defense and the added aesthetic information of widening the gap the earthquake causes. The art is good too. I specifically like the water animation and the defense walls.
I do think there were improvements that could have been made that tower defenses can have problems with. One of the biggest problems I had with the game was lack of information. Tower defenses get their fun from strategy and you can't strategize if you don't know anything. This was mainly that I didn't know what the difference between the towers was. It was the same issue with the enemies. My best guess right now is that different towers are better at handling different enemies but there was no colour coordination between them or anything so I'm not sure. The no strategy issue combined with the fact that your money just keeps going up even in-between waves creates tower spam. Besides that there were a couple of minor issues like the towers covering too many squares behind them and the distance you had to cover with walls. I also think I ran into a bug. After a few round I decided to see what happens when you lose. I started readying up without placing more towers but the earthquake would damage my towers without spawning more enemies and after a few rounds of that I couldn't ready up at all.
Overall I liked the design of your game and I'm sure the issues I had were due to time constraints anyways.