Refactoring.
Prepend padding '0' to numbers.
Remove hatching texture.
Don't animate the motion of masks.
Simplify processing options.
Add an option 'row' changes the initially focused row.
Add change_query_string() function.
Now change_query_string() takes an object as a set of key-value pairs.
Separate get_data() from save_data();
Rename 'permalink' feature to 'export' feature.
Add a function 'set_data()'.
Fix set_data() so that it can correctly overwrite panels' states.
Add an option 'memory' for loading, saving and clearing pixel data.
Fix typos.
Automatically save the pixel data for resuming.
Distinguish specifying empty pixel data and not specifying pixel data.