Thanks for playing and trying it out! It wasn't Firefox that let you down, it was me! Haha, For some reason I liked the click to move (not hold) and seriously should have added alternative movement styles!
Overscoping is certainly a classic game jam challenge--I had hoped to add "levels" and a tutorial, and just do more balancing (snake speed, mole speed, detection areas, map size, etc). I almost wish I had spent more time on balancing that on the ancestor features, but hearing you liked them makes me feel better!