Crystal Quest is a classic game from the 1980's that's been ported to Steam. It's designed to be controlled with an old-school trackball mouse. So on the Steam Deck it's a bit challenging to control. I settled on tweaking a mouse profile on the right trackpad. It's not as perfect as an actual trackball mouse, but it's definitely very playable. Outside of challenging controls, the game runs like a dream on the Steam Deck.