I'm not very happy with this one. It is almost a brute force solution using syncs, with a good amount of time lost as a result of that. However, it does save time whenever it is given 2 or more H2 in a row, taking regular time for all other inputs. There must be a better solution than this.
Recorded solution for "Danger Zone" from SpaceChem, a design-based puzzle game from Zachtronics Industries.