Use PCB soldering to adapt a Mega Drive pad to MSX
My Ultimate 3DO had games on an SSD but no controller. I build an RP2040 USB to 3DO adapter, flash Joypad OS and finally play.
A box of open source retro PCBs from PCBWay, from Amiga RAM expansions to an UnoCart 2600, each one a future project for the channel.
The Atari 7800 deserved better controllers. I build a small adapter that lets you use a Sega Mega Drive pad on the 7800, then put it through some games.
Plugging a Mega Drive pad straight into a C64 can kill the CIA chip. I build an open source adapter that makes it safe, and works on the Amiga too.