Running is also a survival skill . . . (after all, it doesn’t say you must kill things for 60 seconds, only that you must survive…)
Hmm, this looks like the first place where you are really given a choice of where to go next. Levels along the road continue the main progression line, levels not along the road are optional, they give more practice, more challenge, and more gem earning opportunity.
Among the optional levels are two types that lend themselves to returning to . . . repeatable levels and multiplayer levels. The repeatable levels get harder every time you submit and succeed, so you may need better code and/or better equipment to succeed again (don’t be fooled by the cheaters with really high scores, on the repeatable levels I don’t think there is a legitimate score above around 7-8 tops). For the multiplayer levels once you beat the simple AI, your code goes into a “ladder” and competes with other peoples code (and equipment, so to speak) . You of course come back when you have better equipment and/or coding ideas. You are able to work on your code directly against a submitted opponent of your choice or watch any two submitted opponents compete. (see here)
I’d suggest that nothing be purchased until you must, to be able to continue. This will help you and your students not make unwise purchases, that halt or slow down your future progression. The whens of items becoming available for purchase has recently been tweaked to help in this regard, but prudent spending is always advised.