Loop (Pentomino Walls) (702)

Other names: Loop around pentominoes

Shade some cells, and draw a single loop that passes orthogonally through centers of cells.
The shaded cells must form the shapes of pentominoes (contiguous regions of five cells). Pentominoes cannot touch along edges or corners. One cell from each pentomino is given in the grid, and the shape of that pentomino is identified with the letter. The letter-to-shape correspondence for pentominoes has been supplied for you. Rotations and reflections of a pentomino are considered the same shape.
The loop must go through all unshaded cells and cannot go through any shaded cells. The loop cannot enter the same cell more than once.

Reference: WPF (1)