Each practice game builds a different set of rooms, with corridors, alcoves and more than one way through. Yellow wallpaper, a lit ceiling, and doors that stay shut until the maths is right.
- Walk with W, A, S and D. The arrow keys turn and move as well.
- Click the view and move the mouse to look. On a phone, drag the right-hand side of the screen, and use the pad on the left to walk.
- Stand in front of a door and press E, or tap Door. A real door asks a question. Some doors do nothing.
- Chairs, cabinets, desks and other objects are tucked into the rooms. Four of them have a digit scrawled on them. The rest are blank.
- At the way out, the keypad lists those objects in order. Type the four digits in that order, then walk through.
- Easy, Medium and Hard change the size of the level and the maths. Today’s rooms are the same for everyone until midnight UK. Practice is a new map each time.