A screen is a moment. A system is what makes the next hundred moments coherent. Before adding components, we map the decisions the product needs to make: what deserves emphasis, what can be scanned, what happens when data is missing, and how the interface explains a change of state. These decisions become tokens, patterns, and language before they become pixels. Good foundations reduce the number of choices a team has to make from scratch. They also make exceptions easier to spot. When a new feature needs a new color, spacing rule, or interaction pattern, the system gives us a useful question: is this genuinely new, or have we missed a pattern we already need? Design systems are not museums of polished parts. They are working agreements between people. Keep them close to the product, document the reasoning, and let the system evolve with the questions users are actually asking.