fix: polish pass for traffic, nav, icons, contact email reveal and dashcam robustness

tests/unit/traffic.test.ts

@@ -1,23 +1,53 @@
 import { describe, expect, it } from 'vitest';
 import {
   HERO_CAR_HALF_WIDTH,
+  TRAFFIC_BODY,
   TRAFFIC_FADE_LENGTH,
-  TRAFFIC_LAMP_HALF_SPACING,
+  TRAFFIC_LANE_JITTER,
   TRAFFIC_LANES,
   TRAFFIC_NEAR_Z,
+  trafficLamps,
   trafficNearFade,
   wrapTrafficZ,
 } from '@/scene/world/traffic';
 
 describe('expressway traffic stays clear of the hero car', () => {
-  it('keeps every lamp outside the car body, with lane jitter', () => {
+  it('keeps every body outside the hero car, with lane jitter', () => {
     for (const lane of TRAFFIC_LANES) {
-      const half = lane < 0 ? TRAFFIC_LAMP_HALF_SPACING.fast : TRAFFIC_LAMP_HALF_SPACING.slow;
-      const innerLamp = Math.abs(lane) - half - 0.25; // 0.25: max lane jitter
-      expect(innerLamp).toBeGreaterThan(HERO_CAR_HALF_WIDTH);
+      const inner = Math.abs(lane.x) - TRAFFIC_BODY[lane.kind].halfWidth - TRAFFIC_LANE_JITTER;
+      expect(inner).toBeGreaterThan(HERO_CAR_HALF_WIDTH);
     }
   });
 
+  it('never lets bodies in adjacent lanes overlap, and keeps them on the road', () => {
+    const spans = TRAFFIC_LANES.map((lane) => {
+      const half = TRAFFIC_BODY[lane.kind].halfWidth + TRAFFIC_LANE_JITTER;
+      return [lane.x - half, lane.x + half] as const;
+    }).sort((a, b) => a[0] - b[0]);
+    for (let i = 1; i < spans.length; i++) expect(spans[i]![0]).toBeGreaterThan(spans[i - 1]![1]);
+    for (const [left, right] of spans) {
+      expect(left).toBeGreaterThan(-8);
+      expect(right).toBeLessThan(8);
+    }
+  });
+
+  it('runs each lane at one speed, so no vehicle drives through another', () => {
+    const xs = TRAFFIC_LANES.map((lane) => lane.x);
+    expect(new Set(xs).size).toBe(xs.length);
+  });
+
+  it('puts every lamp on the vehicle body', () => {
+    for (const kind of ['car', 'truck'] as const) {
+      const lamps = trafficLamps(kind, 0.5);
+      expect(lamps.length).toBeGreaterThanOrEqual(3);
+      for (const lamp of lamps) expect(Math.abs(lamp.x) + lamp.w / 2).toBeLessThanOrEqual(TRAFFIC_BODY[kind].halfWidth + 0.01);
+    }
+    // A readable pair: two tail lamps mirrored at one height.
+    const [left, right] = trafficLamps('car', 0);
+    expect(left!.x).toBe(-right!.x);
+    expect(left!.y).toBe(right!.y);
+  });
+
   it('is fully dark before the car near field and lit beyond the fade', () => {
     expect(trafficNearFade(TRAFFIC_NEAR_Z)).toBe(0);
     expect(trafficNearFade(0)).toBe(0);