I made Jigsaw Puzzle Timer using touch panel TFT display. Touch Screen Display Shield for Arduino UNO is used to display the time, and the timer stops when the puzzle is completed.
By attaching a copper foil tape to the back of the wooden puzzle, it will become conductive when the puzzle is completed.
Touch Panel TFT Display Shield
Driver is ILI9325. 320 x 240 pixels. I used it as a stopwatch to measure the time to complete the puzzle.