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Chess LLD: Scope Like a Senior, Move Like a Strategy Pattern

A low-level design walkthrough of chess: scoping the unbuildable, one movement rule per piece via the Strategy pattern, a shared path-clear helper for sliding pieces, and the complete implementation.

By fiveyearsdevJune 12, 202611 min read

"Design chess." The final boss of game LLD — and the first trap isn't technical at all. Chess is enormous: castling, en passant, promotion, check, checkmate, stalemate, threefold repetition. Try to build all of it in forty-five minutes and you'll deliver none of it. The first skill being tested is scope: can you carve out a core that's genuinely complete, name what you've deferred, and show exactly where each deferred rule would bolt on? The second skill is the one this series has been building toward. Tic-Tac-Toe needed no patterns. The vending machine almost needed State. Snake & Ladder coll…

What’s inside

Let's start nowhere near a computer

Step 1 — Functional requirements (sentences first, and scope out loud)

Step 2 — Non-functional requirements

Step 3 — Nouns → a deliberately flat cast

Step 4 — The table rules (one gate for every move)

Step 5 — Sliding pieces share one helper

Step 6 — The pawn: three rules in a trench coat

Step 7 — The deferred rules, and why they're cheap now

Step 8 — Trade-offs (each one keeping an NFR)

The complete implementation

The interview corner

Where to go from here

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