As has already been mentioned, I struggled to play on a laptop (a MacBook actually). I couldn't even use my tools at all, left clicking, right clicking, I toggled the guide box on (the red tile square), and still I couldn't use my axe or the pickaxe? Didn't encounter any lag though?
The graphics are gorgeous and I love some of the cutscenes too. Keep up the great work, it's going to pay off!