Hi, I want to build a simple electronic circuit for a college project.
It should be analog or mixed (not entirely a digital circuit).
It must be simple and fast to build but not as simple as an op-amp voltage comparator.
It must work!!! Especially at the exam time.
I want the circuit diagram and component numbers of the circuit, along with tips, a photo of the circuit maybe, ….
Please, suggest one such circuit, and don't tell me about electronics sites where I can search for circuits

I want to diy an electronic expriment. It's about number keyboard and seven segment. If you press '0~9' or '.' ,it will show number or '.' on the seven segment, and pressng * will clear the seven segment. Now, I don't know how to design the circuit diagram, please help me.
What i want to do is not using computer, but on electronic board, which often used on experiment.