I'm really sorry for the negative experience bug, but if you get a lower amount of experience than before, it was because I changed the formula to gain experience. The new formula make experience harder than before to gain. If you got a negative amount of experience on reset, it should be fixed now.
Sorry for the inconvenience, and thanks for playing! :)
The Kumon solution book sacrifices explanation for . A student doing 10 related-rates problems in one sitting, each with a fully worked solution, will eventually internalize the pattern even without reading a single explanatory sentence. This is Kumon's behavioralist strength—and its cognitive weakness.