By around Day 3 of using the excellent web site, Gamestar Mechanic, the students get challenged and highly engaged as they play through the various episodes and learn game design
Each episode has several missions on it. Some of the missions get harder as they go, especially the time challenges
I try to tell the students that they should beat the level themselves, as it is so gratifying when they truly EARN the sprites/avatars that can be used in their own games in the future
If only more things were set up in the classroom where we give the students short obtainable goals, such as defeating a boss or solving a puzzle. From what I have seen this week, my students have been engaged and challenged, but they get really excited when they actually beat the level and earn what they need to make their own game.
If you want to make your own video game using Gamestar Mechanic, check out one of my previous posts that has links to my Prezi lesson plan, student samples and other instructions