Flapjack

📖 Strategy guide: How to sort Flapjack in par: count the gaps, then close them

How to play

You have a stack of pancakes of different widths, in the wrong order. Tap a pancake: the spatula goes under it and flips it together with everything above it, so that part of the stack ends up in reverse order. The pancakes below do not move. That is the only move there is. The stack is solved when the smallest pancake is on top and the largest is on the plate. On a keyboard, the digits 2 to 7 flip that many pancakes from the top. Fewer flips is better, and the par is the fewest flips that can solve the stack.

Daily, levels and challenges

The daily puzzle has seven pancakes, is the same for everyone and changes at midnight UTC. Easy has five pancakes. Hard has six burnt pancakes: each one has a dark burnt side, every flip also turns the flipped pancakes over, and the stack only counts as solved when it is sorted and every burnt side faces down. In Hard you can tap the top pancake, or press 1, to turn it over on its own. ⚔️ copies a link to the exact puzzle so a friend can try to match your flips. ↶ undoes a flip, ↻ restarts.

How the puzzles are made

Each puzzle is a shuffle produced from a number, the seed, so the same seed always gives the same stack. A breadth-first search over every possible arrangement then finds the fewest flips that sort it, and that number is the par. Shuffles that are too quick to solve are thrown away and shuffled again. Sorting pancakes with a spatula is a real mathematics problem: nobody knows a simple formula for the number of flips the worst stack of a given height needs. For seven pancakes it is eight flips; for six burnt pancakes it is twelve.

Tips

• The simple method takes two flips per pancake: bring the largest unsorted pancake to the top, then flip it down into place. It always works, and it rarely makes par.
• Look for pancakes that are already neighbours in size and avoid putting the spatula between them.
• To beat the simple method, find flips that create a new pair of neighbours without breaking an existing one.
• In Hard, a pancake that goes down with a flip lands with its top face down, so get the burnt side on top first.