Exponent Exchange

Create a 64-value tile, open the central seal and leave escrow empty within twelve exchanges. Tap two neighboring cells to swap them; swapping with empty space is allowed. A horizontal or vertical line of three or more equal values collapses into value × 2^(line length−1). The upgraded tile lands at your second tapped cell if it belongs to the line, otherwise at the line’s first cell. Cascades repeat without new tiles or gravity. Any collapse containing or bordering the central seal opens it; the sealed center cannot be swapped before then. Escrow mode lets you lift one tile into a reserve, then deposit it into an empty cell later. Each lift, deposit or successful swap spends one exchange. Use escrow to stage a powerful line rather than wasting swaps. No-match swaps still consume time. Keyboard: Tab and Enter/Space operate buttons; R restarts.