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Buttons (556)
Instruction:
The grid is full of dark and light buttons. When a button is pressed, its color changes (from dark to light or light to dark), as well as any buttons directly above, below, left, and right of it. Press exactly [three] buttons with [a letter] on them, so that all the buttons become [white]. (Buttons that have the same symbols on them are not connected in any way.)
In the actual puzzles, the words in the brackets will be replaced with other terms.