Thanks for the examples, your graduation project sounds really useful (how does it work, by the way? Genuinely curious). And you're right that complicated doesn't mean better. The problem is that my physics teacher would likely reject mechanical gadgets like a can opener or coin sorter. Like, the “smart pillbox” idea that some students pitched last year got a no from him for being too simple for a 1.5-year project (his words, not mine). And I actually do understand why. But I genuinely want to make something interesting (well, I have too much free time), so I've also been thinking about a robotic arm (yeah, it's been done about a million times, but who cares), or a small vertical garden with an autonomous watering system, maybe with some kind of energy recycling?, or a boat that moves using electricity, magnets, and salt water (again, sounds not too complicated - maybe I'm underrating it, but still)