Very very nice!! A beautiful and polished game. Mousy menu but it's ok ;) My main suggestion would be to lower the prices or raise the gains. After all, it's a small jam game and people won't play it for hours. Cheaper upgrades, and/or some different mushrooms giving more money would be nice.
There could be for example a blue mushroom moving a little faster (or slowing) and giving 2 coins. And most upgrades would benefit from a 50% discount I think!! This way, more people would play long enough to see everything you coded with care and love :)
In any case, great game, congratulations!!