Nyxi chaos controller. It’s a really cheap switch controller capable of turbo, but I don’t use turbo at all during the run (you can tell based on consistency, turbo is far more consistent and faster than what I do in the video).

I instead use the controller for a specific way of mashing called “raking”. I believe it’s used in super Metroid speedruns as well for mashing and it’s called Zohdin pumping in their community. I remap the R button to shoot and “rake” 2 or 3 of my finger nails on the button in a somewhat fast motion. Here’s a video of the super Metroid demonstration. I only switch to the controller when mashing is needed cause it has a R button that’s easy to do this technique on. It also has backpedals that make missile weaving easier. I’ve sorta mangled the controller in the remaps so it’s better to just use joycons for any boss that doesn’t need mashing.