Thanks so much for the thoughtful feedback. Fixing the spikes was a priority for us and we already fixed it. It no longer uses the full square as the collision mask (it was using the default tilemap collision mask), which wasn't fair because the spikes come to a point. So, we made the spikes a separate sprite and created a custom collision mask for them. These new collision boxes follow shape of the spike and are actually smaller and more forgiving.
The actual level is being redesigned. Since we rushed to get it out for the game jam, we didn't spend any time testing the balance. The new levels will be more balanced, with difficulty that ramps up gradually. We will also implement checkpoints to reward players for their progress.
As for the controls, we are adding more ways of playing, including mobile controls. But we will be adding more keyboard configurations that align we standard practices.
We aren't sure why the music volume is doing up and down. We didn't experience this, but I'll look into it. Could you elaborate a bit more on this issue? Did you notice a difference in volume between the intro, stage and ending music or was the stage music on its own fluctuating in volume? Also, thanks for the suggestion of keeping some forward momentum when letting go of the jetpack button. We'll keep that in mind.
Thanks again for playing our game and for your suggestions. We really appreciate it!