Pentominoes: Twelve Pieces
Pentominoes: Twelve Pieces is the digital take on the century-old packing
puzzle. Twelve pieces, five square cells each, must lie inside a rectangle so
that no cell stays empty and no two pieces overlap. Simple — until you meet the
X piece, which has exactly one orientation and only a handful of possible
homes.
The pieces are named after the letters they resemble: F, I, L, N, P, T, U, V,
W, X, Y, Z. Together they cover 60 cells — exactly the area of every board:
6×10, 5×12, 4×15 and 3×20. Each size changes the character of the task: 6×10 is
the classic and the best entry point, while 3×20 is a long corridor where a
mistake in the first columns ruins everything.
Controls are built for the phone: tap selects a piece in the tray, a board tap
places it, tapping the selected piece again rotates it, a long press mirrors
it. No pixel-perfect dragging — just taps, one action at a time. On desktop
it is the same with the mouse.
Inside there is an honest solver: the demo does not replay a recording but
fills the board live with an exact backtracking search pruned by a
reachability check. Want a hint — run the demo mid-solve and watch where the
AI puts the next piece.