Parity Blocks
Place every piece. Keep every row and column even.
Place every piece. Keep every row and column even.
Place every piece onto the board. Pieces can't overlap or hang off the grid, but you don't need to fill every square. Empty cells are fine.
The puzzle is solved when every row and every column has an even number of filled squares.
Count squares, not pieces. A U-shaped piece that covers 2 squares of one row and 3 squares of the row below adds 2 to the first row and 3 to the second.