AngryBirdsLogic.js layers the game onto the Wave 0 solver: wood/stone/ice
plus TNT with distinct density, friction and fragility; damage as a health
model with crack stages rather than instant shattering; all 8 birds with
one ability per shot; scoring, stars, win/lose, and a stepSim -> events[]
contract the scene replays as FX.
The load-bearing discovery is that damage must read approach velocity, not
the solver's accumulated normal impulse. The accumulated value carries the
static load of everything stacked above: measured 3.4e5 at the base of a
10-block stone tower, above the threshold that should shatter wood. Wiring
damage to it makes tall towers quietly crush themselves at rest, and it
reads as a level-design bug rather than a physics one. prestep now also
publishes contact.impactImpulse — the momentum needed to stop the approach,
zero at rest by construction. Resting fell to 2.4e4 against real hits of
1.9e5 to 2.7e6, and the whole material table was calibrated by measurement.
AngryBirdsGame.js maps the 2400x1080 logical level through fixed sx()/sy()
helpers at scale 0.78 rather than zooming the camera, which keeps HUD text
in plain screen coordinates. Slingshot drag, ghost trails of previous
shots, level select, star tracking and progress persistence are in. A
follow-camera is deliberately deferred to Wave 5 — it is pure presentation
and cannot be validated headlessly.
Six starter levels ship as the Poached Eggs opening. All stand unaided,
none damage themselves on load, and a greedy aim sweep clears every one.
Registered as slug angrybirds, iconFrame 92, under Video Games.
tools/verifyAngryBirds.js -> 114 checks green. Peggle (909) and Excitebike
(620) still pass; Goo Tower's 2 failures are pre-existing and unrelated.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M1wNRvLLtyfCDAET7oYouf
Angry Birds is fundamentally a rotating rigid-body stacking game, and
neither existing engine could be extended into it: PeggleLogic collides a
moving circle against static pegs with no rotation, and GooTowerLogic has
no angular state at all because its rigidity is emergent from
triangulation. Matter.js ships in the CDN Phaser build but is not
importable in bare Node and not reproducible, which would forfeit the
verifier, the generator's measured star thresholds, and the editor's
winnability gate.
AngryBirdsPhysics.js is a bespoke solver: convex polygons and circles,
uniform-grid broadphase, SAT with reference-face clipping to 2-point
manifolds, sequential impulses with warm starting keyed on stable feature
ids, Coulomb friction, split-impulse position correction, and island
sleeping.
Split impulse rather than plain Baumgarte is the load-bearing choice.
Biasing the real velocity makes penetration proportional to load, so the
bottom contact of a 10-box tower sank ~9x deeper than the top and the
stack sagged 12.85px. Correcting position through a discarded
pseudo-velocity removes a fixed fraction of the excess per substep
regardless of load; sag is now 0.46px per contact, exactly the slop band
we deliberately allow.
Gate: 10-box tower settles in 0.68s and sleeps with <1px drift and 0.35
degrees of tilt; friction holds on a 15 degree slope and slips on 40;
replay is bit-identical and frame-rate independent; 40 monkey seeds
produce no NaN, no overspeed and no sinking.
tools/verifyAngryBirds.js -> 51 checks green.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M1wNRvLLtyfCDAET7oYouf
Brian Fertig