Death to px, long live ch

CSS pixels are logical units that may map to several device pixels on high-DPI screens, while CSS centimeters rarely match physical centimeters, yet 16 px looks consistent across phones, laptops, and TVs. The author sizes text containers with `min(75ch, 100%)` and scales padding, margins, and occasional vertical spacing using `ch` and `ex`, replacing percentage-based layouts with character-based measurements without abandoning pixels entirely.