Advanced Aerial Robotics Made Simple

This one is my favorite, a 'cyclocopter':

https://www.youtube.com/watch?v=JoVmejDsMrM

I don't care as much about the combat as about the efficiency.

That's a big wing airfoil, and it's cheap foam, and it's not as mechanically complex as a helicopter. There is potential here for low-speed heavy lift. I wish they'd included a scale-up of batteries from "Tiny" to "Too heavy to loft", with sustained in place hover times and watts per kilogram as the performance metric.

It’s a really interesting project, worth checking out the video where he merged it with a companion computer to do computer vision tasks and inject controls straight into the flight controller https://m.youtube.com/watch?v=uaY2G5Kbj_g

That was freaking cool.

He also has a fun YouTube channel: https://m.youtube.com/playlist?list=PLTSCOv-lGtMax-oA4Pnq8OT...

One of the first flight controllers he coded was in Arduino..

https://github.com/nickrehm/dRehmFlight/tree/master/Versions...

He deliberately kept the code in single file and made sure it was still easy to follow.

Oh yeah, this'll scratch an itch.