itch.io

You misunderstand. Buying promethium now and skipping days doesn't do anything. You had a piece of promethium before you activated hyper training. Activating hyper training consumed the promethium, giving you 20 charges of hyper training in return. Hyper training is not connected to the auto-training, so passage of time does not affect it. The only thing it has an effect on is the manual training done by clicking the Train button.So you'll have to do that to get rid of your hyper training charges to "turn it off". Manual training does cost energy from the energy pods though, so you'll need at least 2 of those to use up the maximum of 20 hyper training charges.

There is no "off" button, because there's no downsides to having hyper training on. It doesn't do anything unless you actually use manual training - in which case it gives you more training for the same amount of energy consumed.