Unfortunatly, the web version suffers from lag during the first second of the boss fight. I guess this is due to the particle effects. A downloadable version is available if you want to plenty enjoy the demo.
Regarding the menu, I gave tips in the description to help the player. Because I have not had enough time to include a lighting for the computer screen (In order to clearly indicate the interaction).
The player can unlock up to 4 skills using dedicated mods. As i mentionned, time was running out , so no mods which unlock skills are implemented (my bad). I took a lot of time (too much for sure) thinking about this concept, the mods and their bonus.
By the way, you can also jump. Control the height of your jumps by releasing the key.
For the music, you can turn it off thanks to the options menu. You can also reduce the combat sound effects, the ambiant effects and the master volume. For this latter, using + and - keys allow you to control the volume. I am sad.. I try my best whitling the theme. (But ok, i admit it, this is weird :). But this is aberration gamejam.)
Thank you vm for your time, giving me a nice and detailed feedbacks. That's really helpful.