Hello and welcome to Feedback Quest 9! My name is Hythrain, and I'm one of the hosts for this lovely event! I'm also one of the streamers, so both the game and this feedback are being done live! If you want to see the see the VOD, let me know and I'll link you to it when it's uploaded to YouTube!
So I'll admit I don't know if this game is featuring real isotopes. I know that thoron, a name you use for several isotopes, is actually just a commonly used name to refer to a specific isotope known as Radon-220, but beyond this I can't say. If this game is named on real isotopes, that's cool.
There are two primary complaints I have about the game, both stemming from the early game. The first is that players are forced to read a bunch of text instead of being taught the game in a more organic way. The more text a player has to read before they start playing, the less they're going to remember. Working this into the gameplay in a guided tutorial would be better, especially one that explains things like what the various numbers related to each isotope even mean and how to utilize shielding, cooling and ejecting.
Second, I felt like the game can start very slow due to the long half-life of the starting isotope. I think it'd be useful to have a function that lets the player alter the game's speed, both to speed it up and to slow it down, so that they can control things better.
Some other issues I had were that I found myself just not using the elements meant to absorb heat from other cells. it just felt so inefficient to me compared to just having stronger cooling systems in each cell. I also was really annoyed at the fact that I had to keep scrolling all the way down the elements list to what I wanted instead of the game remembering the last element I had put in and keeping the menu there when I went to put something new in. The last thing to annoy me was how isotopes start to cause a money loss once they have so little mass. Considering the idea is that elements will decay into other elements, having this function of the player losing money makes no sense because it discourages them from letting the isotope decay fully. And speaking of losing money, why do I lose money if I have no isotopes in my cells? That made no sense. I thought it might've been a bug, but even after I filled a cell and ejected it I was still losing money.
Overall it's a great concept, but I feel it needs some improvements to make it more fun to play.