Dmitri Mendeleev's periodic table looks simple, it doesn't strike as if the elements are, in fact, significantly different from one another. But when you dig in and understand that just a 'seemingly insignificant' property of the number of electrons and protons makes for a vast difference in the way each element acts and reacts in proximity to others - you get a taste of how a harmless looking list can hide all the relevant complexity.
Interactive elements in web design, such as checkboxes and radio buttons, have a similar deceptive simplicity. While they may appear to be just arrangements of frames, icons, and text, there is actually a lot of complexity involved.
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