Great demo! I'm looking forward to the full game.
Only a single tiny complaint: when you fall down to a new floor, the totem sometimes spawns right below you, so it gets activated before you can move. It's not too important but it sucks when you waste a golden one. Something as simple as delaying the totem spawn 1 second would fix that.
I had one crash when claiming the reward of Floor 2 guardian normal (could be a browser thing though). I can also confirm the game lags when monsters explode on Firefox.
And as a final bit of feedback, I would like for the skill tree to have a bit more of depth. Right now it's just a straight line which barely feels like you are making a choice. Maybe merge all the skills into one large tree with their paths crossing every now and then, so you can jump from one to another and skip the skills you don't care about.
Anyway, good job :)