Start a room on the TV. Everybody goes to the address on the screen (or scans the code) and types the 4 letters. You get a blanket fort with a wall of couch cushions around it.
Open the toy box: pick 2 of the 4 toys you're offered. Put your launchers down inside your wall. Battle: tap the room on your phone to shoot. Everybody shoots at once. Fix your fort: drag on your phone like a trackpad to slide your piece, tap to turn it, PLACE to put it down. BEST SPOT puts it somewhere good for you.
If there's no fort inside your wall when the bell rings, it's bedtime (the first night's free). You don't sit out: you play the house (the dog, the Roomba, Will's Mom, or Dad).
The snack bowl, the remote, the lamp, the mini fridge full of thin milk, the cat (who sits on your launcher). Wall them in and keep them. Extra forts count too.
The sleepover guests go to sleep in the coziest fort: big, snacks, pillows, no milk on the floor, nobody's mom saying things. Every guest asleep in your fort when the bell rings is a point. Most points wins.
Sock Balls never run out. Every night you pick two toys from the toy box: Thin Milk, Will's Mother, The Darkness, the Grant Wouldn't, a guinea pig (they're herd animals), the kickball, water balloons, the Whoopee Cushion, a call to Roadhouse... The stuff in your fort gives you more, and sometimes the milkman comes.
If your wall touches somebody else's (even at a corner), it's one wall. Everything inside it is both of yours, and you split the guests. Break the wall apart and you've broken up.
Once a night you can hand down a piece you don't want (the Giant U, the cushion with the hole) to somebody else. Some pieces misbehave: the dog gets up and leaves, Grant rolls over, the beanbag slumps.
The keys are on the screen next to your fort. Player 1: arrows, Enter, Right Shift turns it, / jumps to a good spot (or the next fort to shoot at), M hands it down. Or just use the mouse. Player 2: WASD, Space, E, Q, R.
Type the 4 letters on the TV.
Drag anywhere on the room to slide your piece. Tap the room to turn it. BEST SPOT finds a good place for it (tap again for another).
Tap the room where you want to hit. Your closest loaded launcher fires.
Pick 2. You get two of each (one of the rare ones).