1. A debugging user interface implemented by at least one computing device, the debugging user interface configured for: enabling a user to start and stop playback of a portion of code that was logged as the code was executed, where the logged portion includes values of variables that are in scope of the logged portion of code; enabling the user to move forward and backward to any line of the logged portion; and presenting to the user the any line along with the values of the variables as they were at the a time that the any line was executed.