A puzzle producing an image with each colour is used exactly once.
Generated initial project via: spring init -d=web,devtools,thymeleaf --description Image Puzzle -g pjw -n puzzle --package-name pjw.puzzle -a puzzle
To run: mvn package && java -jar target/puzzle-0.0.1-SNAPSHOT.jar and navigate to http://localhost:8080/
Prerequisites: java (1.8+) maven