Alright some feedback time. The game seems pretty decent, I like the feel overall.
The biggest thing from my brief play session was that I'd like to be able to just apply dice to whatever grid I'm hovering over by pressing a relevant number key. So hitting 1 on the keyboard should just drag and drop the die that's in the first slot onto the grid. Slay the spire does a similar thing and it definitely speeds up the gameplay there.
Second I'm not a huge fan of checking a hidden attack/defense value then doing some mental math. I think you can keep everything the same where you have the enemies stats and die rolls show up when you hover over them... But perhaps show outcoming damage for the turn somewhere directly. So if a lizard guardman or whatever is attacking me twice just show a "4" somewhere.
A minor gripe at the start it's hard to tell what you can actually interact with from the main menu until you hover over it. I didn't know I could select what dice bag I wanted to use until... well until I started writing this and double checked it. I like the asthetics though. Just somehow find a way to make it more clear you can select the hero character down there.
Also for the test version maybe write for the other dungeons "Not avalible yet" and have a very handy, "Click me" button or something over it. Cause for someone jumping in here it's a little confusing trying to enter multiple dungeons and it just not working for 2/3. For me the crypt is the one I clicked last.
Being able to preview the dice in the dice bag select from the main menu would be nice.
I didn't like the way energy was shown. This one is definitely preference though, not sure how I'd change it. It's functional and does look nice though. Maybe make the used energy even darker? Not sure I just stumbled a few times, especially when it came to higher cost energy dice that I wasn't expecting to cost 2.
It was a little unclear at first that you're supposed to click "Fin" to activate the board and the reroll button is something I forgot about that I really shouldn't have. I'm a little dumb though so that might be okay. Maybe brighten the letters, outlines on both of them? Like make the hover effect the standard so they're more lit up and have them turn gold or something when you hover over them?
Speaking of the "Fin" button having a check for if you try to activate the board when you have no dice slotted like an, "Are you sure?" might not be amiss.
I can't speak for a lot of balance for the game because I only played some runs for the first few floors. I was a little confused when I upgraded dice at the end of combat and then got a random die afterwards. I thought I was upgrading the dice I chose into a new random die. Probably want to make it a little more clear with a small animation or something that your die of choice is being upgraded AND THEN you're getting a new die afterwards.
A lot of this is small polish stuff. Your game definitely has a good asthetic and solid core gameplay loop.