The thesis proof: examples/gamemaker/resources/fixtures/racing.splash is a
complete playable racing game in 72 lines (12-corner oval from a waypoint
loop, 4 cars, gates, standings, restart) with no physics, no AI and no lap
bookkeeping in script. Blocks run engine-side at 60Hz: Blocks::pre_step
(intent -> motion) before step_world, post_step after; Blocks is Clone and
snapshots beside GameWorld so a failed eval rolls both back together.
- game.car (4 suspension raycasts on a box3d rigid chassis), game.character
(drives the existing mover sweep + owns idle/walk/run blending),
game.plane; game.drive/autodrive/speed
- Brains: game.wander/chase/patrol/caught — the fixture's hand-rolled AI,
absorbed engine-side
- Race kit: spawnpoint, checkpoint, place, race, standings, lap/rank/
finished, score/score_of (Shared-tier data, ready for replication)
raycast_vehicle audit (defects documented in car.rs, still live in xr):
libm sin/cos in steering (unreplicable), a wrong side-impulse denominator
(iaj.dot(iaj) where it should be (I^-1 aJ).aJ), and an unguarded division.
Kept the structure, replaced Bullet's friction solver with an arcade force
model: suspension acts at the contact point, grip and drive through the
centre of mass, steering as yaw torque — no lateral force can generate
roll, so it is stable by construction rather than by roll_influence fudge.
Engine bug fixed at the source: GameWorld::new() left rng at 0 and
xorshift64* is a fixed point at zero, so rand() returned 0 forever for any
world built through the sim API. reset_content seeds on every eval, which
hid it from gamemaker entirely; found by a wander brain that never left home.
Tape probe byte-identical; racing fixture evals clean and drives (AI follow
the line, gates bank in order).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
