Tetroscope (437)

Locate some tetrominoes (contiguous regions of four cells) in the grid. Each piece of a tetromino occupies a single cell. Tetrominoes do not touch each other, not even diagonally (that is, if two tetromino pieces are in adjacent cells, they must be part of the same tetromino). The same tetromino cannot appear more than once. Two tetrominoes are considered the same if one can be rotated to match the other. (Reflections are considered different.)
Some numbers are given at corners of the grid, which must match the number of cells touching that corner that are part of a tetromino.

Reference: WPF (1)