the idea is really cool, but it's incredibly frutrating to not being able to c check & mate the oppenent, and even if it is possible, the RNG render it nearly impossible(different maps, not always the upgrade needed, sometime to early because you don't have the points, etc), and when you start having a build to allow you to check & mate, you usualy reach the required score to win, so you have to restart everything from scratch, it could be cool to push the limite for longer gameplay, and eventualy check & mate the AI, appart from that, the idea is good
I should probably add some sort of confirmation to the final event to indicate that the game ends when you click it. You can keep playing as long as you like if you ignore it. The game could probably be a couple of matches longer, and maybe it could be fun to have a requirement of scoring a couple of checkmates before it ends. Checkmates are hard to get, but they feel pretty great when you manage to set one up. I want to add some sort of scoring system to give players more of a reason to play again, and checkmates will probably be a big part of your score.