Introduces a new "bonus item" system alongside the existing smashables:
- **Gameplay**: Floating collectible prizes (CTC box, guitar, cash) that the bus passes through with zero physical response. On first contact, the item pops (scale-up + fade) and spawns a radial burst of tinted firework particles that arc down under gravity, settle on terrain, and fade out. Each collected item scores 100 points on the end-of-level tally.
- **Config**: `BONUS_ITEM` in `config.js` holds all tuning knobs (particle count, speed range, spin, lifetime, per-type tint palette, pop scale/duration). `SCORE.perBonusItem` added.
- **Entity**: New `BonusItemManager` class owns static sensor bodies for each bonus item, detects bus collisions, and orchestrates the pop + firework burst animation. Particles are real Matter bodies exempted from bus/kid collision so they can land on terrain without affecting gameplay.
- **Editor**: "Smashables" section renamed to "Placeables" with a kind toggle (Smashables vs Bonus items). Bonus items are float-only with no gravity option. Preview map, click-to-place, item list, and export all support both kinds. `splitPlaceables()` in `levelBuilder.js` splits the unified editor list into the two level arrays (`items` / `bonusItems`).
- **Levels**: Levels 2–6 updated with bonus item placements (and some additional smashable items).
- **Assets**: New `bonus-items.png` spritesheet (9 frames: 3 bonus items × [item + 2 firework objects]) registered in the asset manifest.
- **Score screen**: `_revealBonus()` method in `LevelScoreScene` displays collected bonus count and points, skipped when zero.
Add four new section types to the level editor:
- dropOff: instant vertical drop with gentle downward tail
- gap: flat lead-in, x-gap, flat landing at same height
- lip: flat run into a steepening (t²) kicker ramp
- dropGap: like gap but landing is well below takeoff
Fix Terrain physics body generation to extrude straight down from
segment endpoints instead of using rotated rectangles. A previous
perpendicular-offset approach caused near-vertical segments (dropOff
cliffs) to balloon physics bodies sideways under adjacent terrain,
making the bus ride above the drawn ground.
Update level03 ("Mind the Gap") to use editor-generated terrain data.
Generalize levelBuilder smoothing to detect gap-shaped sections
(structurally via takeoffPoints/landingPoints) rather than by type
string, so future gap types work automatically.
- Add `timeLimit` configuration to levels 1-4
- Implement countdown timer that starts when throttle is pressed
- Display remaining time in HUD, turning red when under 10s
- Add 'time-up' failure condition and message in LevelFailedScene
Brian Fertig