Great work, I like the Undertale vibe in the graphics and storytelling... I half expected to find ice creams along the way that would FILL ME WITH DETERMINATION.
It took me a while to understand the gameplay though (actually I got it when reading a comment on the itch.io page). It should maybe be made clearer that the sun and colored body outside the play viewport are actually related to the gameplay (the sun could maybe turn to a quiet moon when you go in cool chambers).
And yeah, diagonal movement would be nice :) But not having it adds to the difficulty, that's also fine with me.