There are two modes to V is for Vortex: Story and Freeplay. Unfortunately, other than the fact that there's a one page cut scene at the beginning of story mode and in freeplay mode you can start at whichever level you like, there really is no difference between the two modes. The idea behind the game is that you're trying to get through a series of rooms. To do that you must use this gun you've found that creates two types of portals – a blue one and an orange one. Functionality-wise there appears to be no difference between the two types of portals.