The game should pause when you go in the menu. Other then that, it's a great game. It's not intuitive though and it's a bit difficult to figure out. I think people will grade it lower for that. But the game itself is solid! Just needs a bit of polish.
Some buys. I'll submit a bug report but a) sometimes enemies remain on screen once you've killed them and b) if you exit the level up screen without using a talent point you lose it. Needs a bit more polish to become a very very good game!
I beat the 78th level at level 88 by the way and it was still a bit of a challenge. Can't way for gemcraft2! I might go back and play gemcraft1 again for a bit in the mean time.