Design the object model and transport state machine for a video queue player: the layer that decides what plays next as a user queues clips and controls playback.

Operating context. One player instance, single in-process service. The player holds an ordered play queue of video items and exposes transport states (idle, playing, paused, buffering, ended). Repeat mode is off, one, or all; shuffle is on or off. Users enqueue items, play a specific item now, and skip to the next or previous item; the player auto-advances when a clip finishes. A bounded history lets 'previous' walk back through recently played items. The media source signals buffering and end-of-media events, and the player reacts to them.

Out of scope. Video decoding and rendering, adaptive bitrate and network transport, casting to external devices, DRM, and any UI widgets.

What to produce. The class hierarchy (player, play queue, video item, repeat and shuffle strategies), the transport state machine, and the next-item selection rule. Be explicit about: the state machine's legal transitions and the events that trigger them, how repeat and shuffle compose to pick the next item, how 'previous' uses the bounded history, and how auto-advance on end-of-media is driven by an injected event rather than a real player.