Dark Star is a secret ending for Unpacking. Instead of placing items normally to achieve a gold star at the end of each level, you want to place each item incorrectly, where it would have a red outline around it in a normal playthrough. Placing every item incorrectly produces a black star at the end of each level.
General Tips: -Some items count as being placed correctly if they are right along the foot of the bed, so be mindful of that. Books are fine along the foot of the bed. -Shoes can surprisingly be placed in a lot of locations, but usually it's guaranteed that they can't be placed along the edge of a room, or on a bed. -Clothes can go under a bed, but hangers cannot.
You also have to unplace items that are already pre-placed when you start a level. Here is a list of items that need to be unplaced in each level:
1997 -None
2004 -Hangers in the bedroom closet
2007 -Hangers in the bedroom closet -Post-it note on bulletin board above bed -2 gray figures in the dining room
2010 -Literally everything that is already placed except for these items in the living room: CD stand, all dumbbells, and all items on the wall
2012 -Literally everything that is already placed in both rooms, including items in drawers and cabinets in the bathroom
2013 When placing items in 2013, be conscious about the fact that things will be rearranged in 2015. -None
2015 -Bath mat in tub -Cleaning fluid and trash bags in cabinet under sink in the kitchen -Unplace anything that got placed correctly from new furniture being added. Places to check: bedroom closet, living room shelves, office desk
2018 -None