This level occupies the map slot MAP01. For other maps which occupy this slot, see Category:MAP01.
MAP01: Zero Day, designed by Cyb, is the first map of MassMouth 2.
Strategy
Walkthrough
The level starts with a cutscene. Ontras troopers (Ontras armed with rayguns) attack the moon base and approach The Worm. MassMouth then comes out of his bedroom to see what's going on. A screen appears with the silhouette of an unknown villain. After he says a few words, The Worm is teleported away, and the Ontras try to kill MassMouth.
Now you take control over your character. You only start with your fist, but you can go back to your room to get some energy ray cells. Kill your enemies and take the blue keycard. Go to the room next to the landing strip and open the door with "MassMouth" written in front of it. Walk outside. End of the level.
After you finish the map, a text screen informs you that The Worm is still probably on the moon, but you have no idea where he is.
Secrets
There are no secrets in this level.