RelicWorld

A live outdoor environment is the most hostile design surface there is: no level designer authored it, GPS drifts by the second, and the map doesn’t know which side of a fence you’re on. The engineering challenge isn’t the game — it’s turning raw, noisy sensor input into an interaction layer that is fair (objectives never land somewhere unreachable), safe (play stays away from traffic and private property), and deterministic (the same physical action always produces the same state), all without backend authority or an asset pipeline.

RelicWorld is where I worked that problem — progressively evolving an iOS prototype from a simple coordinate-proximity check into a three-phase spatial state machine.

RelicWorld began as WorldTag, an earlier iOS spatial prototype, and was later revisited as a more structured location-based gameplay system. The rebrand — naming only, no gameplay change — marks the shift from spatial-tagging groundwork toward a playable capture-the-flag application layer. Residual “WorldTag” references in the repository are historical.

The world model is a set of nested spatial containers with hysteresis buffers on every boundary — the structure that makes noisy GPS behave like a stable game state.

What keeps the machine legible is a deliberate separation between three kinds of state, each with a single owner.

The phases map cleanly to the loop: Explore (.pursuing) approaches with coarse guidance; Trigger fires on chamber entry — auto-pickup, hazards placed; Escape (.carrying) routes toward the nearest zone-boundary exit, and crossing it while carrying lands .completed.

The decisive lessons came from walking the prototype around an actual block, not from the simulator.

• Dual hysteresis for boundary jitter. Field testing exposed heavy GPS noise: at any container edge the state would flap on and off many times a second. The fix was asymmetric hysteresis buffers — a 5 m exit buffer on the outer zone and a 3 m buffer on the chamber — so you enter at the line but only exit after meaningfully leaving. Crossings became deterministic instead of jittery.
• Route polylines as a placement proxy. Rather than fetch a separate road-class dataset, placement reads geometry already in hand — sampling the MKDirections walking-route polylines and scoring candidates by connectivity and segment length to favor walkable, mid-block positions. It’s a pragmatic heuristic, not ground truth (route proximity isn’t the same as walkability), but it removes a whole data dependency and keeps objectives off yards and out of intersections in practice.

The throughline of RelicWorld is the same one in the rest of this work: take a messy, unpredictable human reality — here, raw physical movement through unauthored space — and engineer it into something intentional, fair, and safe to interact with. The substance is the systems architecture: a clean state machine, a layered separation of state, and field-hardened heuristics that survive contact with real GPS.

Captured on-device while walking the prototype around a real block — showing zone reveal, carrying state, and retry lockout without exposing live coordinates or identifiable map detail.