Open Field, a 10x10 Patches puzzle
Arrow keys move. Enter starts a rectangle; arrows resize it; Enter places it. Escape cancels. Delete removes a patch. Control or Command Z undoes.
About this board
The first 10x10 opens with a 28, a 4x7 field that fills the top-right and is fixed from the start, along with a 10 that lines the entire bottom row. Everything else is fitted around those two: a 9 down the left edge, a wide 12 in the lower half, and a scatter of small 2s and 3s in the middle where most of the actual thinking happens.