Pretty good tower defense game! It even has all the sounds and music and everything, which is a rarity in a game jam (not slagging anyone who didn't get audio working, short time frame is short!).
I'd say rework your UX so that a player isn't clicking in multiple places. The game doesn't seem so fast that you don't have the time to process selecting a tower type while spawning. I do like the random placement, but going between selecting to spawn and the type seems kind of weird. Maybe even just having a random type of dice that gets spawned, and allowing more merging. What I'm saying is that there's a lot of different ways you can take it if you wanted to evolve the concept more. to make the gameplay a little smoother!