The portal is a block in which the player needs to get to. It is always changing colour, giving a magical effect. When the player enters the portal it starts to spiral outwards. The background also fades away in a blue haze until everything disappears altogether and the completion of the level is announced.
Sometimes when the portal has spiraled enough and then the player dies, the portal finishes its cycle before the player respawns and the player gets to the next level. The developer has stated "There must be medics on the other side :D"