i have the 2026 Steam Controller, playing through Firefox 153.0.1 on Arch Linux. testing a DualShock 4 worked fine
edit: i left my old SN30 plugged in for long enough for it to turn on, and it works fine there.
i really liked this, i wasn't initially ready for a "restart the whole thing until you do really well" so it threw me for a bit. ended up with something like 650 seconds clear time, 11 death, 2500 green energy. and not having to listen to Reagan from across the map is one of the greatest feelings in the world.
for some reason, the web version seems to detect my X button as Y, and Y as X. for reference, i'm using a Steam Controller that was getting mapped to a standard XInput gamepad. A and B weren't swapped.
the standalone Linux version doesn't exhibit this problem, so i don't know what it might be. unfortunately, i don't have a standard XInput controller to test with.