In Japan the puzzles (not this one) are “Samunamupure” but a UK newspaper decided adding arithmetic to Sudoku made it a “killer,” and the “Killer Sudoku” name stuck. We call them “Killer Cages” three decades later. No cages in this puzzle, but each tiny arrow defines a “virtual cage,” so it’s a “Little Killer” puzzle. I don’t choose the names!
The key strategy to Region Sum Lines involves lines that are a single cell in one region but three cells in another region. Three and one at the same time. So here’s a puzzle with nine such lines!
Plenty of blue Region Sum Lines all around, plus one of each digit. In case you need a reminder of the digits one through nine!
Given digits can be friends! Who needs lines or dots or cages when you have great big digits? Well, great big digits and a global constraint.
Sometimes a puzzle is less about what goes where, and more about what doesn’t go there.
The rain is gone! I can see all obstacles in my way. Gone are the dark clouds that had me blind. It’s going to be a bright, bright Sudoku day.
The azul sky out the windows puts on in the mind of a beach in Mexico. How many windows? Uno, dos, tres, quatro!
What time is it? Four-thirty. It's not late, no. No! It's early, early.
It’s a computer chip. Or a mockup of a computer chip. Transistors, traces, and so on.
The coloring is cosmetic. More or less.