There's a short explanation on the board you're looking at when the game starts. You have create a hideout somewhere in the level with the E key, then collect and store all items in it (there are four in total). You can collect all items at once or indiviually; you drop them with the Q key. You can also create new hideouts whenever you want but you can only have one at a time, and all items must be stored in the hideout simultaneously to win. If other balls come near your hideout, it gets destroyed.
Basically we wanted to give the players a lot of freedom to choose the route they can take - so it would be interesting to watch in a speedrun.
Thanks for playing! :)