I recently made a short and simple shoot 'em up video game, I had a lot of fun thinking about enemy behaviour and coding the logic behind it.
You can download it via this link (just put '0' for the price and it will let you download it): https://gumroad.com/l/Sbjbv
The playthrough video is here: https://www.youtube.com/watch?v=AUsdi2j2GO8
Hope you'll have fun!