### double pendulums

swing togeteher or perish

```Canvas.setpenopacity(-0.1);

const N = 40; // min=5, max=40, step=1
const M = 50; // min=10, max=100, step=1
const L1 = 50; // min=10, max=90, step=1
const L2 = 50; // min=10, max=90, step=1
const delta = 0.03; // min = 0.01, max=2.0, step = 0.01
const d_max = 5; // min=1, max=15, step=0.1
const dt = 0.03; // min=0.01, max=0.1, step=0.01
const g = 2.5; // min=1, max=20, step=0.1

const turtles = []
const phi1 = []
const phi2 = []
const speed1 = []
const speed2 = []
const done = []

const m1 = 1, m2 = 1

for (let i = 0; i < N; i++) {
turtles[i] = new Turtle();

phi1[i] = []
phi2[i] = []
speed1[i] = []
speed2[i] = []
done[i] = []

p1 = Math.random() * 2 * Math.PI
p2 = Math.random() * 2 * Math.PI

for (let j = 0; j < M; j++) {
done[i][j] = false

phi1[i][j] = p1 - delta/2 + delta/(M - 1)*j
phi2[i][j] = p2 - delta/2 + delta/(M - 1)*j
speed1[i][j] = 0
speed2[i][j] = 0
}
}

function walk(i) {
let n_active = 0

for (let i = 0; i < N; i++) {
if (! done[i][0]) {
n_active++

let not_done = 0
let x0 = 0, y0 = 0

for (let j = 0; j < M; j++) {
if (! done[i][j]) {
not_done++

let prvx1 = L1 * Math.sin(phi1[i][j])
let prvy1 = L1 * Math.cos(phi1[i][j])

let prvx2 = prvx1 + L2 * Math.sin(phi2[i][j])
let prvy2 = prvy1 + L2 * Math.cos(phi2[i][j])

let p1 = phi1[i][j], p2 = phi2[i][j]
let o1 = speed1[i][j], o2 = speed2[i][j]

let omega1 = (-g * (2 * m1 + m2) * Math.sin(p1) - m2 * g * Math.sin(p1 - 2 * p2) - 2 * Math.sin(p1 - p2) * m2 * (o2**2 * L2 + o1**2 * L1 * Math.cos(p1 - p2))) / (L1 * (2 * m1 + m2 - m2 * Math.cos(2 * p1 - 2 * p2)))
let omega2 = 2 * Math.sin(p1 - p2) * (o1**2  * L1 * (m1 + m2) + g * (m1 + m2) * Math.cos(p1) + o2**2 * L2 * m2 * Math.cos(p1 - p2)) / (L2 * (2 * m1 + m2 - m2 * Math.cos(2 * p1 - 2 * p2)))

speed1[i][j] += omega1 * dt
speed2[i][j] += omega2 * dt

phi1[i][j] += speed1[i][j] * dt
phi2[i][j] += speed2[i][j] * dt

let newx1 = L1 * Math.sin(phi1[i][j])
let newy1 = L1 * Math.cos(phi1[i][j])

let newx2 = newx1 + L2 * Math.sin(phi2[i][j])
let newy2 = newy1 + L2 * Math.cos(phi2[i][j])

if (j == 0) {
x0 = newx2
y0 = newy2
}
else if ((newx2 - x0)**2 + (newy2 - y0)**2 > d_max**2) {
done[i][j] = true
}

turtles[i].jump(prvx2, prvy2)
turtles[i].goto(newx2, newy2)
}
}

if (not_done == 1) {
done[i][0] = true
}
}
}

return (n_active > 0) && (i < 10000)
}```