Highscore of 126. How far you get beyond 100 points seems mostly luck-based.
The visuals are really good, and it looks very arcade-ish. The tetris-like experience is very engaging and I've tried multiple times to get a better highscore.
The arrow on the side scrolling down seems to suggest that multiple operations could happen down the stack when you drop one number, but I haven't seen that happen. (I don't think that it's possible.) Any + signs on the bottom are also doomed to do nothing, which is a bummer. For the sake of recursion, I would've loved to see that!