Furniture arrives in groups
The engine places the whole set: sofa, rug, coffee table, armchairs facing the centre and a TV opposite the sofa. Bedrooms get a bed with nightstands, kitchens a dining group, studies a desk. A group is placed or rolled back as a whole, so you never get a table nobody can sit at.
Doors and cabinets keep their space
Every door keeps a 45 cm clear strip on both sides, and the area the door leaf sweeps stays empty. Wardrobes, dressers, kitchen units and the fridge keep 60 cm clear across their full width, so every door opens. Chairs get 50 cm behind them so you can pull them out.
Twelve layouts, one winner
Each room gets twelve layouts, and each is scored for problems: a walkway that is too narrow, furniture bunched against one wall, a corner you can't reach from the door. The one with the fewest wins. It then gets 120 small tweaks: slide a piece along the wall, turn it 90 degrees, swap it for another that fits. A wardrobe against a wall only slides along it, and chairs move with their table.
The washing machine finds a spot even in a tiny bathroom
A 3 m2 bathroom in an old Soviet block has no room for a washing machine, so it goes next to the kitchen sink, or into the hallway if the kitchen is full too. A one-room flat with no bedroom gets a bed in the living room. A kitchen-living room is furnished as both: the kitchen run first, then the sofa and TV, and a dining table from 24 m2.
One room or the whole flat
"Furnish room" fills only the selected room and leaves the neighbours alone. Handy when you've arranged the bedroom yourself and want a quick draft for the kitchen. The room gets the same layout it would get as part of the whole flat; "Shuffle" gives you another.