I liked the idea of combining a dungeon builder with a card game, and the graphics and music are nice.
However, I think this game lacks some polish and indication of what's going on. For example, I'd like to know exactly where the hero will spawn and where the exit is so that I can place my mines accordingly. Looks like there is a cooldown system - I think, it would be nice to have a clearer indication of not having enough. Sometimes I felt like it's placing units I didn't intend to place, which got me confused for a moment.
Also, for me nothing happened after defeating the hero. Dunno if it's a bug or not.
Anyway, making a game in 48 hours is tough, so congrats!