Frist of all- the animation is great. You don't see IK used in game jams that often, and here it's used to a great effect. Sound fits too- sounds are clear and intense. I liked it!
The gameplay could use some polish and variety. The game lets you aim up, but there was no reason to do it! Some zombies attacking from the roof maybe? The game could ramp up faster too- make the upgrades cheaper, but the difficulty growth faster! This would keep the player at their toes :)
I found the idea with the radio interesting- in a wave based game you rarely decide when the waves end and start. I think this idea could be developed further. What if the rewards grow as the wave lasts longer? Something to think about :)