Waaaaaay too many ads. At 30 seconds a pop, a 10x10 puzzle would take roughly 3000 seconds (50 minutes) if you got every single one wrong. A 15x15 would take just under 2 hours. Fortunately it doesn't take THAT long but with all the ads (one every time you get one wrong after 3 attempts, or when you want a hint), it feels like 5x that amount. At some point I will lose it (my patience) and uninstall it. It's one of those games where THEY get paid (ad revenue) when YOU make a mistake...