I teach high school robotics and our introductory course uses Arduinos as the microcontroller. While I do like the Arduino Web Editor as they have fixed some of the bugs over the last couple of years there is one problem to the free version. There is a daily limit on compiler time and sometimes students run up against that limit, usually as they are about done solving the problem they have. I like everything else about the IDE as we use Chromebooks at our school which precludes using the desktop software. I tried Codebender but it is limited to 30 lines in a sketch. Does anyone have another alternative they have found?