Harrow & Finch have sent you to take the measure of Lammas House. It reads as a house: wallpaper, floorboards, a lamp in every ceiling, the sun going down outside every window. Then you walk north, east, south and west, and the fourth door does not bring you back.

Every room is really there. Doors you open stay open, as many as you like, and you can stand in one room and look through two doorways into two others that cannot both be where they are.

Come back each day and find the day's documents behind a chain of keys, then leave by the door you came in. The house is different every day, and a little less patient.

Letters, research papers, photographs and a child's crayon drawings are hidden in drawers, cupboards and lids, and kept from one day to the next. Nobody tells you what happened here. The pieces do, if you find them.

A little girl lived here, and she knew the house better than anyone. Her toys open the rooms she kept to herself.

Nothing hunts you while the time lasts... Or does it?

• First-person exploration in impossible, non-Euclidean space -- seen, not just mapped

• Sunlit, ordinary, and wrong: no gore and no monsters in the walls

• A seven-day campaign, and a ten-day mode once it is done

• Three difficulties: Chill, Usual and Dread

• English and Portuguese (Brazil)