Considering you hade significantly shorter a time compared to others, it's really impressive what you manage to achieve - that's not to put this down, it's impressive even if you had the full amount of time, so to do it in less you should be proud.
To give some light criticism, I think separating controls from keyboard to mouse hurt the playability alot - if the controls were all mapped to the keyboard (or mouse), you'd have a lot easier time switching without. That, and the inability to rotate the camera hurts the game a bit I think (apologies if I'm just stupid and missed how haha), it's difficult to see where the towers and and stuff.
That being said - that's just nit-picking for an otherwise really well-designed and enjoyable game :)