Great Single Button Games

[XoPachi]

What are games that purely use a single button (of course beyond movement inputs) and get a ton of depth out of just that?
My favorites are Kirby Air Ride and Mars Matrix.

[Steven]

Super obvious answer, but Sanic Hedgeheg 1/2/3&K/CD. Mania uses a separate button to transform, so that can't be counted.

[guigui]

One Finger Death Punch and its sequel OFDP 2 may be worth mentionning here.

They are 2 buttons, but no directionnal input at all. One button hits baddies on the left side of the player, and the other hits baddies on the right. Add to that a lot of baddies, stylish kung-fu moves, precise gameplay, weapons, "do not button mash", great SFX, and a cat for the weirdest mode and you have an excellent simple but demanding game.

[Stevens]

Gyruss
Burger Time
Crystal Castles

[AGermanArtist]

I really like Downwell on Switch (2) with the screen vert orientated.
Knightmare on MSX has also been a firm favourite with me since its release. I still play it regularly.

[BrianC]

Star Trigon

[orange808]

Arkanoid and Buster Bros

[jonny5]

Star Trigon

Beat me to it. Awesome little game, I used to have the PCB.

[SuperDeadite]

X-Multiply