유용한 사이트

Json syntax check

http://jsonlint.com/

Shell script syntax check

https://www.shellcheck.net/

online photoshop

https://pixlr.com/editor/

gradation list

http://uigradients.com/#WhatliesBeyond

Web scripter

http://colorscripter.com/

Algorithm Visualizer

http://algo-visualizer.jasonpark.me/#path=backtracking/knight's_tour/basic