Hi. Don't beat yourself up, 3 hours(or even 5) are both much and not that much. It's still a great game and surely, a lot of space to expand it :)
I don't like the time-limit puzzle, because you can't make puzzles too complicated because timie limit itself and it might take a lot of tries to get it right.
But if they're fairly simple and it's just about when and where use items available, i think it's good. But if you want to make more complex puzzle it might not work