Author: Andrey Bogdanov
Shade exactly four connected cells in each outlined region. All shaded cells should form a single connected area without 2×2 groups of cells entirely shaded black. Shaded cells in each outlined region form a tetromino (L, I, T, or S) and two tetrominoes of the same type shouldn't share an edge.
Grid control: Click the mouse button at the selected cell to change the filling of the cell. More details about grid control are at the help page.