Author: Vladimir Portugalov
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 color of the cell. Second click will put auxiliary cross sign, which doesn't affect correctness of the solution, but helps visually. You can also drag the content of one cell to another with the mouse. More details about grid control are at the help page.