An error in the code that has an unintended side effect.
Difficulty 0 | Bite Sized
Good for newcomers; relatively easy and rewarding to fix.
Difficulty 1 | Easy
A relatively easy issue, can be solved with a little Google know-how.
Difficulty 2 | Medium
A harder issue that likely involves a larger introduction of code to source and documentation reading.
Difficulty 3 | Hard
Challenging and may involve quite a bit of time to ensure working behavior.