Oooh, this was so much fun, loved the mechanics being introduced over time. The ability to stretch the mask surprised me, but was super intuitive and really opened up possibilities in overcoming puzzles (would be interesting if one of the puzzles required you to shrink after growing).
I enjoyed the SFX, and agree that adding some background audio would definitely help with world building. Even some soft non-intrusive soundscaping / nature effects could go a long way in complementing what is already such a cool and interesting art style.
The masked title font is awesome btw, really cool and fits the game so well.
Awesome job :)