At the start of the puzzle the traveller is at the front, left, bottom cell in period one. The objective is to get to the top, right, back cell by period five. Using the radio buttons the traveller can move up/down, left/right, in/out and also forwards and backwards in time. It is possible to avoid obstacles simply by moving around them or by travelling forward in time until the wall no longer exists or back to a time period before the wall was created.
You will not be allowed to travel forward/back in time if the corresponding cell in the next/previous time period is occupied by a wall.