for (i in 0...particles.length) {
    var p1 = particles[i];
    p1.vx += p1.fx*dt;
    p1.vy += p1.fy*dt;
    p1.x += p1.vx*dt;
    p1.y += p1.vy*dt;

    p1.fx = 0;
    p1.fy = gravity;

    p1.d = p1.dNear = 0;

    p1.vx = fastMax(-velCap, fastMin(p1.vx, velCap));
    p1.vy = fastMax(-velCap, fastMin(p1.vy, velCap));

    if (p1.x < h) {
        p1.vx -= (p1.x-(h-wallSpring*p1.vx))*wallDamp;
    } else  if (p1.x > sw-h) {
        p1.vx -= (p1.x-(sw-h-wallSpring*p1.vx))*wallDamp;
    }
    if (p1.y < h) {
        p1.vy -= (p1.y-(h-wallSpring*p1.vy))*wallDamp;
    } else  if (p1.y > sh-h) {
        p1.vy -= (p1.y-(sh-h-wallSpring*p1.vy))*wallDamp;
    }

    for (j in i+1...particles.length) {
        var p2 = particles[j];

        var dx = p2.x-p1.x;
        var dy = p2.y-p1.y;
        var d = Math.sqrt(dx*dx+dy*dy);
        if (d < h && d > 0) {
            p1.springs.add(new Spring(particles[j], sCreateLen));
        }
    }
}

for (p1 in particles) {
    for (sp in p1.springs) {
        var p2:Particle = sp.p;

        var dx = p2.x-p1.x;
        var dy = p2.y-p1.y;
        var d = fastSqrt(dx*dx+dy*dy);

        var fThreshold = sp.restLength*sBreakYield;
        if (d > sp.restLength+fThreshold) {
            sp.restLength += plasticity*(d-sp.restLength-fThreshold)*dt;
        } else if (d < sp.restLength-fThreshold) {
            sp.restLength -= plasticity*(sp.restLength-fThreshold-d)*dt;
        }
    }
}

for (p1 in particles) {
    for (sp in p1.springs) {
        var p2:Particle = sp.p;
        var lij = sp.restLength;

        if (lij > h) {
            p1.springs.remove(sp);
            continue;
        }

        var dx = p2.x-p1.x;
        var dy = p2.y-p1.y;
        var d = fastSqrt(dx*dx+dy*dy);

        var f = kspring*(d-lij)/d;
        var fx = dx*f;
        var fy = dy*f;

        p1.vx += fx;
        p1.vy += fy;
        p2.vx -= fx;
        p2.vy -= fy;
    }
}