Thanks for the feedback.
Yes it is a short game, and was not really meant to be a long game. This was mostly just a small side project.
About the information on upgrades and skills, you're definitely right. It would probably be a good idea to add some sort of hover-over tooltip, with a more detailed description of the upgrade/skill. Personally I like the idea, of the player wondering about what the "next" upgrade does. But a purchased upgrade should probably tell the player what it actually does.
Being able to switch number formats makes good sense. I've added that to the backlog.