It's ok, the art is nice, the gameplay is very simple, I get it, it's a demo. I'd suggest at the very least it should offer something more, so far it's just clicker heroes clone reduced to like 6 or 7 monsters and 6 upgrades. So at the very least a new mechanic should be added so it's like "Clicker heroes with a twist".

It can be a good game, this demo is a solid base, but it all depends on what the dev does next.