Roadmap

Workspace layout: shared/ (wire types), server/ (authoritative sim), client/ (render terminal). The platform layer — window, GPU, input, RGB332 palette — lives in the external pbio crate (git dependency), not in this repo.

Achieved milestones

TGA loader: Image, from_tga, to_tileset, decode_rle in client/src/assets.rs
Pixel helpers: set_pixel, extract, blit, blit_tile in client/src/game/pixelhelper.rs — signed i32 offsets, clip against all four framebuffer edges, index 0 = transparent
Input system: GameAction, InputMap, InputState in client/src/input.rs (over pbio::Key)
Protocol spec: notes/protocol.md — Header, State, Action, Chunk, Entity, EntityQuery, EntityDetail, Ping/Pong; reliability model
Shared crate: packet structs as bytemuck::Pod with compile-time size assertions, player_action / packet_type constants, chunk_id / chunk_coords
Server binary: 24 Hz tick loop, 3×3-chunk test world (build_world), wall collision, per-client action queue, ChunkPacket dispatch on cache miss, stale-client eviction
Client net: NetClient in client/src/net.rs, non-blocking UDP recv, StatePacket / EntityPacket / ChunkPacket / PongPacket dispatch, entity-checksum retransmit
End-to-end loop: player moves on server, position reflected in EntityPacket, rendered on client
Tile rendering: chunk-based world rendering from received ChunkPacket data (6-bit unpack)
Tick-based movement: movement resolved in entity_tick, currently every 4th tick (sim.rs)
Sprite-based entity rendering: entity type_id → tile in entities.tga, blitted with transparency
Phase-staggered broadcast: per-client send_phase, flat outbound load across ticks
Ping/Pong RTT measurement (PingPacket / PongPacket)
Connection timeout: client emits Disconnected after 10 s without a StatePacket; server evicts clients unseen for 10 s
Map loader: Tiled-CSV parser in server/src/map.rs (flip-flag masking, content-derived dimensions), load_world slices it into chunks, invisible solid border at the map rim. Replaces the hardcoded build_world. See notes/07-map-loader.md
Client movement prediction: queued unconfirmed steps (path in client/src/game.rs), paced at the server's 6 Hz movement cadence, reconciled against EntityPacket positions, dropped after idle timeout. Shared collision vocabulary shared::tile_collidable (currently empty — every tile walkable) keeps client prediction and server sim in lockstep.
Click-to-move: framebuffer click → world tile, A* over the chunk cache (client/src/game/pathfind.rs, unknown chunks count as blocked), route translated into cardinal actions one step per movement interval — the server only ever sees N/E/S/W and stays authoritative. Keyboard input cancels the route; each step is re-validated at send time and a blocked step voids the route. In-flight steps render bright blue, planned route dim blue.

Upcoming work

06 — Hybrid tick loop (partially done)

Design of record: notes/06-hybrid-tick-loop.md (24 Hz base tick + stride scheduling). This supersedes the original 20/10/1 Hz three-tier sketch.

24 Hz base loop (server/src/main.rs)
Phase-staggered broadcast at 12 Hz/client (send_phase in server/src/net.rs)
Stride layout settled: entity_tick at %4 (6 Hz, sets movement rate), broadcast at %2 (12 Hz/client). The 06 note now documents this and why.
Action-point model (energy / speed per entity, act when energy >= ACTION_COST). Removed from entity.rs for now as premature — reintroduce when NPCs (08) actually need it. Then entity_tick can move to %2 (12 Hz) and speed sets the effective movement rate.

07 — Tiled map loader (done — see Achieved / `notes/07-map-loader.md`)

Remaining follow-ups when the need is concrete:

Collision vocabulary: tile_flags in map.rs is currently empty (all walkable). Fill in collidable / opaque tile ids as the level design requires.
Tile flipping: orientation is discarded on load; revisit with the sprite pass (09).
Multiple / object layers (spawns, triggers) — not yet parsed.

08 — Basic NPC entity + AI budget

One dumb wandering enemy. Validates the simulation architecture before complexity accumulates. Depends on the action-point model from 06 being reintroduced.

Add EntityKind::Npc with a think() -> u32 method returning budget cost
Per sim-tick: distribute think_budget = BASE / (clients + 1) across entities ordered by player proximity
Complex entities consume more budget; simple ones less. Loop breaks at zero — natural load shedding.
No framework. No trait objects yet. A match on EntityKind is fine.

let mut budget: u32 = BASE_BUDGET / (client_count + 1).max(1);
for entity in entities_by_player_proximity() {
    if budget == 0 { break; }
    budget = budget.saturating_sub(entity.think(&mut world));
}

09 — Client camera (sprite rendering already done)

Sprite rendering already landed (see Achieved). What remains is the camera:

Smooth camera: lerp between last known and current server position; do not snap (currently player_pos snaps hard to the server position in game.rs)
Store previous + current position per entity, interpolate on render
Camera math is architectural — affects how entity state is stored. Do it before UI.

Later — UI / HUD

Bitmap font renderer: 8×8 glyph sheet TGA, draw_text(frame, font, x, y, color, text) — see notes/04
UI primitives in client/src/ui.rs: fill_rect, draw_rect, draw_hbar — see notes/05
HUD layout (320×240): HP bar + player name bottom 16px, message log right panel
A real clip-rect on the blit primitives belongs here — once the viewport and HUD panels are two distinct regions, the abstraction earns its keep. Not before.

Later — Robustness + auth

Reactive pathfinding: replan from the confirmed position toward the original goal when a route step is blocked or the server diverges from the prediction (currently the route is simply voided)
Auth token handshake: replace source-address identity (auth_token field exists but is unused)
Multi-datagram EntityPacket: server currently truncates at 66 entities (net.rs TODO)
Asset embedding: include_bytes! for single-binary distribution

Later — World depth

Once the simulation architecture is stable and a real level exists:

Doors, interactive objects (server-authoritative state)
Combat: melee range check, HP, death, respawn
Inventory: on-demand via EntityQueryPacket / EntityDetailPacket
Day/night and weather on the slow tick — affect visibility, spawns
Procedural dungeon generation (BSP or cellular automata feeding into the same tile format)

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