⬆️ Bottom-Up Design

Bottom-up design is the opposite approach: start by building small, reusable components first, then combine them into bigger systems.

📖 Top-Down vs Bottom-Up

	Top-Down	Bottom-Up
Starts with	The big picture (whole system)	Small components (individual classes)
Then	Breaks into smaller pieces	Combines pieces into bigger systems
Best for	New projects, clear requirements	Reusing existing code, libraries
OOP link	Plan classes and hierarchy first	Build utility classes, then assemble
Risk	May miss low-level details	Parts may not fit together well

🎯 In Practice

Most real projects use both. Top-down to plan the overall structure, bottom-up when building reusable components. In your exam, be able to describe both approaches and explain when each is useful.