for my last university-level but pre-university computing science course, I needed to do a project (taking up about 1/2 of the year) to demonstrate what we learned in the course. traditionally people selected to make a quiz using VB6. however, past me was overly ambitious and instead of choosing the obvious, I instead decided to build an electronic device that could load quiz files from json and an editor that would allow you to create your own quizzes for the device.
so I spent far too long designing the circuit and choosing all the components. the device had a nokia 3310 screen, gameboy-style button layout, programmer interface, micro usb, avr microcontroller, lithium polymer battery charger/controller, buzzer, status leds... all kinds of over-the-top features. spent around 150 pounds on components and the circuit board, and many hours of my free/study time (luckily I had fewer subjects that year).
components arrived and I got to soldering everything together. first things first, one of the components got really hot and started smoking, iirc it was the buck boost converter. couldn't get anything to work, I think the only thing that did was the battery part of the circuit.
few months later, I find that I got a C in the course.
there are still remains of this project on my github..