Idea #1: my first initial idea was having a shifting puzzle that had a time complexity. The longer the player takes to solve the puzzle or maze the harder it becomes. As the player advances different levels appear and the time complexity becomes shorter and shorter. So for example, imagine if you had to solve a moving rubix cube and after every 3 minutes the rubix cube would shift slightly. After 6 minutes the rubix cube would shift a lot more etc.
Idea #2: Have an app that allows you to easily mash music together. For example, have an app that creates virtual musical instruments and you can gather sounds from different instruments and record them. Such as playing a G chord on a specific guitar and be able to list the chord progressions to actually play a song. The app would also have the ability to save the music you created and blend it with other instruments within the app. Essentially allowing users to be able to be one man bands with an easy interface unlike producing software.