A Calc II volume of revolution problem is a decent stress test for any study app. It has several moving parts: setting up the integral, choosing the right method, sketching the region being rotated, and labeling each stage clearly enough that a student can follow the logic back to the original question. Type that problem into a general chatbot, and you tend to get a wall of text. Somewhere in the middle is the right answer, but the steps blur together, and there's nothing to look at.

Many portable projectors are still too bulky for everyday carry. Aurzen changed that with the ZIP, the world’s first tri-fold projector. It collapsed to roughly the size of a small stack of cards, making it genuinely pocketable.