Design Snakes and Ladders

Design the object model and core APIs for a Snakes and Ladders game engine that runs a single match end to end. The engine drives a linear board of numbered cells, walks a fixed roster of players around it turn by turn, applies jump transitions (a ladder lifts a token forward, a snake drops it back), and stops the moment someone reaches the final cell.

Operating context. One in-process match at a time, driven by a host loop (a CLI or a test harness) that repeatedly asks the engine to take the next turn. The board size, the starting cell, and the set of jumps are all supplied as configuration at construction — nothing is hard-coded to a 100-cell grid. Two to six players each own a single token and move in a fixed rotation. The host owns the randomness source and passes it in, so a match can be replayed deterministically. There is no UI, no rendering, and no persistence between matches.

Out of scope. The board rendering / visual grid, networked or multi-process play, matchmaking and lobbies, AI opponents, undo / rewind of a completed turn, and saving a match to disk. Focus on the in-process object model, not any transport or storage layer.

What to produce. The class hierarchy (entities, value objects, and the engine service), the public API each class exposes, and the state transitions of a match (setup to in-progress to finished) and of a turn. Be explicit about: how the dice is abstracted so a test can force a known roll; how the board resolves a landing cell through zero or more jumps; how the turn rotation and win condition are decided; and how the design extends to variants (e.g. an exact-finish rule, double-six re-rolls, or a jump that teleports sideways) without editing the core turn loop.