Always fun to roll some math rocks! Neat bite-sized experience.

That said, I'd have loved to see a little bit more constant progression, rather than having to kill several monsters before your first upgrade, given that each monster is multiple click-wait cycles (unless you start with an earth or fire die, then possibly a single long, ponderous wait). I started with earth on my first playthrough and correspondingly found myself spending most of my time waiting. There's a definite feels-bad effect when luck stiffs you and you take three 1d20 rolls to kill a 10hp monster.

There's a lot of room here for other upgrades, perhaps with another dice-independent upgrade layer, such as an artifact which flash-rerolls 1's to improve the result or lets you roll with advantage (each roll is actually two rolls but you only receive the better of the two results). It would also be great to rebalance the upgrade costs based on how much DPS they add -- the single most impactful upgrade in the game, going from 1d4 to 2d4 and literally doubling your damage, is also the cheapest (the same price as adding +1 per roll to a 1d20, which is barely worth purchasing).

Would love to see a more fully fleshed out post-game jam game; this could be fantastic fun as a deeper experience.