I haven't had so much fun in years! I still didn't figure out how to generate puzzle layouts, but I wrote a Haskell program to scrape layouts from another game site, so that I could continue on game play development, and worry about layouts later. Haskell is a much older programming language, on which Elm is based.
Anyway, the game is now playable, though it doesn't help you any. It's sort of like filling out a Sudoku puzzle in a newspaper. But I'm working on feedback, and noticing when you've successfully completed a puzzle.
The game is most easily played with the keyboard, but the keypad below the game board makes it playable on touch screens. I have yet done window auto-sizing, so you may have to zoom a bit to get the right size.
I originally called it "Kakuro Master", but I discovered a couple of days ago that somebody has already used that name for a PC product.
The source code is at github.com/billstclair/kakuro-master.
I plan to eventually wrap the game for sale on the iPhone and Android app stores.