I loved the game and the art style! Superb! The UI is also great (aside from the lane selection, as some already noted)
My feedback would be that for a game jam entry it was too many things to understand an once. For example, only by the end of my third run I noticed there are some items available.
The core gameplay loop was also little confusing: I couldn't tell if I send enough of my forces to the lane to defeat the enemies, and at what point and for what I get the scull points and magic points. And if my troops get to the end of the lane they just stand there aimlessly.