Great minimal level selection and transitions! Worm concept is fun.
One semi-soft-lock: if I loop the worm so it gets stuck in itself, I need to exit the level and come back. Would be best to have a restart button appear when it detects this, or automatically reset!
Also I think the level designs are solid but the new mechanics introduced in level 13 should come earlier. Maybe as early as Level 8. The progression feels slow as around level 8 I wrapped my head around the basic puzzle already.