I loved every second of this! The only thing that needs improvement is the camera: seeing it closely tracking the character’s position as I fell down from great heights caused me a bit of motion sickness (I guess I’m just sensitive to it). Also, when I attempted to make that long jump with all those spikes after acquiring the double jump, I would sometimes respawn on top of the spikes. Fortunately, I didn’t take any damage when that happened, so I could safely jump back to a safe position.
All in all, excellent job! And thank you for providing a native Linux build!