NAU Engine

Mac-first Rust/Bevy flight traversal sandbox built around one playable loop: launch from the terrain, deploy the glider, read wind and lift, collect a route of one-shot air gates, land on an island or the world floor, then relaunch or reset.

The current world combines 41 floating islands with a streamed playable world floor. Twelve non-overlapping air gates form a three-gate main corridor plus optional low and high-altitude branches; the top-right HUD tracks unique collections, and Esc opens a compact pause, controls, and quit menu.

Current Playable State

• Launch, glide, steer, dive, air-brake, collect gates, land, recover, and relaunch across floating-island and world-floor terrain.
• Traverse authored updrafts, crosswind lanes, visible airflow cues, and gust-varied wind that affects both player motion and glider response.
• Fly a self-authored player/glider fixture with grounded, launch, fall, bank, glide, dive, brake, landing-anticipation, and recovery animation states.
• Collide with island terrain, cliff bodies, trees, rocks, landmarks, and world-floor terrain; use the central-island reset when a route breaks down.
• Read 41 individually authored island identities through unique palettes, hero landmarks, species-varied trees, dense flora clusters, ruin precincts, geological formations, and water-linked shoreline and waterfall detail.
• Review movement, camera, collision, route progress, streaming, visual readability, fixture integrity, and release performance through measured sim/app evals, screenshot audits, exports, and scripted play profiles.

See the Showcase for gameplay, world scale, UI, and player/glider review captures. The island art-direction contract records all 41 accepted identities and the 123-view review requirement; the island-surface content contract documents generated ecology, ruins, geology, water detail, budgets, and regression coverage. Detailed world-floor acceptance mechanics and evidence live in the decision record, requirements audit, and acceptance report.

Run

Install Rust with rustup. Ordinary development play keeps Bevy and rendering dependencies optimized while retaining debug assertions:

cargo run -- --play

Use release mode for final play-feel and performance review:

cargo run --release -- --play

The first development build is slower because it compiles optimized dependencies; later builds remain incremental. Debug mode enables the diagnostic readout and gizmos:

cargo run -- --debug

Repo-local alias:

cargo naux

Controls

Input	Action
W / S	Accelerate forward/back
A / D	Strafe/steer
Mouse	Look while locked or while right mouse is held
Left click	Lock and hide the mouse cursor
Right mouse	Temporarily enable mouse look
Esc	Open the pause menu; return from controls
Space	Deploy the glider while airborne
E	Launch upward from the ground
Shift	Dive
R	Reset to the central playtest island
F1	Toggle debug gizmos in --debug mode
F2	Toggle collision proxies in --debug mode

Air gates score once per session and disappear after collection. The HUD and pause menu show the same authoritative total.

Verification

Core Rust checks:

cargo check --all-targets
cargo fmt --check
cargo test
cargo clippy --all-targets --all-features -- -D warnings

Representative measured tooling (jq is required by the aggregate scripts):

./tools/dev_play_performance_gate.sh target/eval/dev_play_performance
./tools/camera_continuity_gate.sh target/eval/camera_continuity
./tools/manual_play_profile.sh target/eval/play_profile/manual.json
NAU_PLAY_PROFILE_DURATION_SECS=300 NAU_PLAY_PROFILE_SCRIPT=freeflight \
  ./tools/manual_play_profile.sh target/eval/play_profile/freeflight-5min.json
./tools/eval_sim_suite.sh target/eval/sim_suite
cargo run -- --eval long_glide_visibility --eval-output target/eval/long_glide_visibility
./tools/eval.sh great_sky_plateau_vistas target/eval/great_sky_plateau_vistas
NAU_EVAL_SCREENSHOT=1 NAU_EVAL_ASSET_AUDIT=0 \
  ./tools/eval.sh island_surface_review target/eval/island_surface_review
./tools/player_pose_preview.sh target/player_pose_preview
./tools/island_art_direction_gate.sh target/eval/island_art_direction
./tools/island_hero_gallery_gate.sh target/eval/island_hero_gallery
./tools/world_content_gate.sh target/world_content_gate
./tools/terrain_export.sh target/terrain_export
./tools/visual_content_export.sh target/visual_content_export
./tools/wind_visual_export.sh target/wind_visual_export

The island art-direction gate requires accepted full-profile signatures, exact per-island feature and tree/rock budgets, one matching hero landmark per island, unique palette and aggregate signatures, correct water-story presence, and authored-feature coverage. The hero-gallery gate requires near, mid, and traversal captures for all 41 islands, producing 123 screenshot/marker pairs with visual and semantic audits; hero probes come from generated mesh triangles, waterfall framing shares the rendered placement, and the gate is included in the world-content gate.

The development-play gate runs the same full-content native scenario in debug and release, enforces frame-time ceilings, and rejects debug builds that drift materially behind release. The camera-continuity gate covers deterministic 30/60/120/144 Hz and hitch contracts plus native mouse, reset, collision, obstruction, and floor-boundary scenarios. World content, development performance, and camera continuity are required by the macOS CI workflow.

Release comparison and world-floor regression gates remain available through ./tools/perf_baseline.sh, ./tools/world_floor_full_gate.sh, and ./tools/world_floor_candidate_gate.sh. Human release play remains part of acceptance after behavioral changes; the linked acceptance documents define the full contract.

Resolved diagnostic note: a host-specific Apple Silicon presentation hitch was isolated below NAU gameplay and required no game workaround; the probe and evidence live in tools/frame_hitch_probe.

Docs

• Architecture
• Project Status
• Eval Spec
• Island Art Direction
• Island Surface Content
• Flight Mechanics
• Roadmap
• Showcase

Principles

• Keep the playable loop small and measurable.
• Add debug visualization before complex behavior.
• Prefer Bevy-native systems until a measured limitation appears.
• Keep traversal constants visible and easy to tune.
• Avoid raw Metal unless profiling proves it is needed behind a clear boundary.