# Concordia 3D Gate 3 — Vorthas and Second Skin

Entry: `/concordia/index.html?mode=3d`. Defeat the Sentinel, then select **Challenge Vorthas**. The challenge starts with fresh arena health and will. Menu restart repeats the current encounter with the same seed.

## Boss encounter

Vorthas reads the original boss stats and owned skills. Phase one alternates Unfinished Blow and Magma Sweep. At the existing half-health threshold, the shared `evolveBossUnit` transformation restores Second Skin health and applies the original stat multipliers and skill list. Phase two cycles Crowned Roar, Second Skin and Unfinished Blow. A brief transition cancels outstanding attacks and prevents casts from spending will; movement and dodge remain available.

Close blows use a directional arc, sweeps and pulses use finite circular areas, and roars use a narrow direction. Ground warnings and the compact enemy meter identify the incoming attack. The procedural boss grows and gains wings in phase two. Final realistic rigged art remains a later integration.

Damage, elemental rules, skill accuracy, unit stats and seeded random draws are shared with tactical combat. The extracted evolution helper preserves the tactical engine's existing transformation. Both impacts commit before outcome evaluation; player death takes precedence and prevents boss revival. First-phase lethal damage can trigger Second Skin, matching the tactical rules, and the transformation occurs once.

## Response and rendering

Strike windup is 9 fixed ticks and its complete action is 30 ticks; Black Flame windup is 14 ticks. A 12-tick input buffer accepts one next attack near recovery completion. Dodge can interrupt recovery after damage commits, without rolling back the hit. Arena walk/run speed is 4.8/7.6 units per second. These adjustments apply only to the isolated 3D scheduler.

The compact top display is retained. Joystick movement changes its knob directly rather than triggering React updates for each pointer event. The 297 static scenery boxes are retained in four material instance batches, reducing their draw submissions. Coarse-pointer devices use a pixel-ratio cap of 1 with antialiasing disabled; phone action buttons omit background blur. These reduce rendering work but do not establish measured device frame rates.

## Validation and boundaries

The 3D suite has 17 passing checks covering shared damage and evolution, one-time phase transition, simultaneous death, input buffering, recovery cancellation, attack shapes, MP and cooldown limits, full boss victory, movement bounds, teardown and campaign-store isolation. Complete live-spawn boss combat with arena obstacles replays identically at simulated 30, 60 and 120 render rates. These are simulation-rate checks, not measured GPU frame rates.

Six existing save, exploration, narration and combat-audio checks pass. TypeScript checking passes. The production build and two Worker smoke checks are required before publication. Browser visual QA and actual iPhone performance have not been measured in this session.

The challenge does not read or write campaign saves, rewards, Codex or story progression. The existing story entry remains available from Menu. The offline build contains the updated game chunks.