How can I close the sliding walls


Hint 1 of 4:
You see 3 triangles pointing away from the bottom of the screen. 

Hint 2 of 4:
Moving from 1 triangle to another moves the walls 1 position.

Hint 3 of 4:
You can move to triangles that aren't adjacent to each other.

Hint 4 of 4:
Enter room again. Click 3rd triangle from bottom then 2nd triangle.