Portals will open based on your score, and not the number of insects eaten. To complete a level and move to the next stage through portal, you must pass a minimum score. If you get a high score multiplier, you can eat fewer insects and still open the portal. Score portals will only open the next level in a building. In order to move to a new building, you must solve a Mystery. Note that individual levels are the rooms you play in, while buildings are groups of levels in the same general area. After a portal is opened, you can move to the next level within the building. After completing all levels in a particular building, the next building will be revealed. However you can only access stages in that next building if you have solved the related Mystery.