"""Tessel's first dance: 2 s loop at 120 BPM. Bounce on every beat; arms change shape each beat
(right up, forward pump, left up, arms out). Writes dance.json for bridge/anim.py. Claude Opus 5.5, 2026-10-11."""
import json
from pathlib import Path

ARMS = [  # (left upper, left fore, right upper, right fore) per beat
    ([0.1, 0.9, -0.4], [0.3, 0.6, -0.7], [0.15, -0.35, 0.92], [0.1, -0.2, 0.97]),      # right arm up
    ([0.6, 0.35, -0.7], [0.95, 0.0, 0.3], [0.6, -0.35, -0.7], [0.95, 0.0, 0.3]),       # forward pump
    ([0.15, 0.35, 0.92], [0.1, 0.2, 0.97], [0.1, -0.9, -0.4], [0.3, -0.6, -0.7]),      # left arm up
    ([0.0, 1.0, 0.15], [0.0, 0.3, 1.0], [0.0, -1.0, 0.15], [0.0, -0.3, 1.0]),          # arms out, forearms up
]
keys = []
for i in range(9):  # eighth notes, 0..2.0 s, last = first for a clean loop
    t = round(i * 0.25, 2)
    beat = (i // 2) % 4
    on = i % 2 == 0
    lu, lf, ru, rf = ARMS[beat if on else beat]
    if not on:  # halfway to the next shape
        n = ARMS[(beat + 1) % 4]
        mix = lambda a, b: [round((x + y) / 2, 3) for x, y in zip(a, b)]
        lu, lf, ru, rf = mix(lu, n[0]), mix(lf, n[1]), mix(ru, n[2]), mix(rf, n[3])
    side = 1 if beat % 2 == 0 else -1
    bend = 1.0 if on else 0.25
    keys.append({
        "t": t,
        "pos": {"mPelvis": [0, 0.035 * side, -0.07 * bend]},
        "rot": {"mTorso": [3 * side, 0, 12 * side], "mHead": [0, 7 * bend, -6 * side],
                "mHipLeft": [0, -20 * bend, 0], "mKneeLeft": [0, 36 * bend, 0], "mAnkleLeft": [0, -16 * bend, 0],
                "mHipRight": [0, -20 * bend, 0], "mKneeRight": [0, 36 * bend, 0], "mAnkleRight": [0, -16 * bend, 0]},
        "aim": {"mShoulderLeft": lu, "mElbowLeft": lf, "mShoulderRight": ru, "mElbowRight": rf},
    })
keys[-1] = dict(keys[0], t=2.0)
spec = {"name": "tessel dance", "duration": 2.0, "priority": 4, "loop": True, "loop_in": 0.0, "loop_out": 2.0,
        "ease_in": 0.4, "ease_out": 0.4, "hand_pose": "relaxed", "keys": keys}
Path(__file__).with_name("dance.json").write_text("// generated by gen_dance.py\n" + json.dumps(spec, indent=1))