How to play Shikaku (and how the ribbon changes it)

The rules

A Shikaku grid has numbers scattered across it. Every number must sit inside exactly one rectangle, that rectangle must cover exactly that many squares, and no rectangle may hold two numbers. When every square on the board belongs to a rectangle, the board is solved. That is the whole game.

In MerryWrap the numbers are gifts. You drag a box around a gift so it covers the right number of squares, and the app wraps it. Cover the whole board and the door is done.

Four strategies that solve most boards

Start with the primes. A 5 or a 7 can only be a straight strip, 1 by 5 or 1 by 7, so those gifts have two possible shapes at most and usually only one that fits. Wrap them first and the board opens up.

Work from the edges and corners. A gift in a corner has far fewer legal rectangles than one in the middle. Squares along an edge can only be claimed by nearby gifts, so ask which gift can reach each edge square, and often the answer is only one.

Look for orphans. Any square that only one gift can possibly reach belongs to that gift, and that fixes at least one side of its rectangle. A square no gift can reach means an earlier wrap is wrong.

Count what is left. Near the end, the unclaimed squares must exactly equal the unwrapped numbers. If a gift has a 6 and there are two separate pockets of three squares, something upstream needs to come off. Every MerryWrap board is built from a real solution, so a dead end is always a fixable wrap, never a broken board.

The ribbon twist

Classic Shikaku treats every valid rectangle as equal. MerryWrap does not. Every wrap spends ribbon equal to its outline, measured in inches. A 1 by 6 strip needs 14 inches of ribbon; a 2 by 3 box covers the same six squares for 10. Each board hands you a spool, and the spool is sized from the intended solution, so a board is always solvable within its ribbon. Wrap wastefully and you run out before the last gift.

Three settings decide how tight that spool is. No Ribbon is classic Shikaku, and the first week of the calendar plays that way. Cozy gives you the solution’s ribbon plus a little slack. Just Enough gives you exactly the solution’s ribbon and nothing more, which is where the last week of December lives.

Playing well with ribbon

Prefer squares and near-squares. For any number of squares, the shape closest to a square has the shortest outline, so a 3 by 4 beats a 2 by 6 and a 2 by 2 always beats a 1 by 4. When a gift can be wrapped two ways, the boxier one is almost always the ribbon-safe one.

Read the cost tag before you let go. While you drag, MerryWrap shows how many inches the box will use and turns the tag red when the spool cannot cover it. That is the moment to reshape, not after.

Ribbon runs out at the end, not the beginning, so spend it deliberately. On a Just Enough board, if you are short by four inches with two gifts left, look for one long strip you placed earlier that could have been a box; that is usually the whole difference.