# Puzzle 80: Doubleback

Here’s a Doubleback puzzle that’s not going to be on the upcoming Polish puzzle qualifiers. The tournament takes place at 12 CET on Sunday and is open to international solvers: competition page, instructions.

# Puzzle 79: Checkered Fillomino

Today marks the start of a series of Checkered Fillominos on croco-puzzle, check them out! (Solving on time will require making an account; they become freely playable after one week. No Java required.)

Here’s an extra one; the croco series starts out a bit more gently than this.

# Puzzle 78: Sukaku

Here’s a puzzle I made quite a while back, I believe the type was on some Sudoku GP round. It’s more puzzle than sudoku. I’m not sure the “different digits” constraint is required to make this one unique, but it should help.

Rules Solve as a standard sudoku. In addition, subdivide the grid into rectangles, such that each rectangle contains exactly one shaded cell, and such that the number in that cell is equal to the area of the rectangle. Rectangles must not contain any digit more than once.

# Puzzle 77: Fractional Fillomino

Here’s a fractional fillomino. Please excuse the lazy rendering, I don’t expect to make more of these.

Rules Subdivide the grid into areas. Numbers within an area must equal the size (in unit squares) of that area. Areas of the same size must not touch along an edge.