You can comfortably play Gemwielders on your Steam Deck by using the trackpad for mouse movement and setting up a simple custom control scheme.
Suggested Control Scheme
- L2: Left Mouse Button
- R2: Right Mouse Button
- A: A Key (adding all defenses or attacking with all cards)
- X: S Key (for inspecting a hovered card)
- B: Space Bar (to move through the tutorial dialogue)
With your right thumb for mouse controls and these key bindings nothing stops you from wielding gems on your portable device.
Touch controls might cause issues in the current state.