public void changeSpeed(SmartblobTri blob, float secondsSinceLastCall) {
   float minSq = minSpeed * minSpeed;
   float maxSq = maxSpeed * maxSpeed;
   for (MovCorner c : blob.allMovCorners()) {
     float dy = c.speedY, dx = c.speedX;
     float speedSq = dy * dy + dx * dx;
     if (minSq <= speedSq && speedSq <= maxSq) continue;
     if (speedSq == 0)
       continue; // rare. it will be pushed on by springs and probably have nonzero speed next
                 // time.
     float speed = (float) Math.sqrt(speedSq);
     float newSpeed = Math.max(minSpeed, Math.min(speed, maxSpeed));
     float mult = newSpeed / speed;
     c.speedY *= mult;
     c.speedX *= mult;
   }
 }
 public void changeSpeed(LayeredZigzag blob, float secondsSinceLastCall) {
   for (MovLine ld : blob.allLineDatas()) {
     if (ld.springTightness == 0) {
       // This is an optimization, not a behavior change, because force is multiplied by
       // springTightness
       continue;
     }
     MovCorner a = ld.adjacentCorners.get(0), b = ld.adjacentCorners.get(1);
     float dy = b.y - a.y;
     float dx = b.x - a.x;
     float distance = (float) Math.sqrt(dx * dx + dy * dy);
     if (distance == 0) continue;
     float wantToAddToDistance = ld.targetDistance - distance; // positive or negative
     // wantToAddToDistance =
     // (float)(2*MathUtil.sigmoid(5*wantToAddToDistance/ld.targetDistance)-1)*ld.targetDistance;
     wantToAddToDistance =
         (float)
             (2 * MathUtil.sigmoid(multParamOfSigmoid * wantToAddToDistance / ld.targetDistance)
                 - 1);
     float normDy = dy / distance, normDx = dx / distance;
     float addToEachMomentum =
         secondsSinceLastCall * wantToAddToDistance * mult * ld.springTightness;
     float addToMomentumY = normDy * addToEachMomentum;
     float addToMomentumX = normDx * addToEachMomentum;
     b.addToSpeedY += addToMomentumY / b.mass;
     a.addToSpeedY -= addToMomentumY / a.mass;
     b.addToSpeedX += addToMomentumX / b.mass;
     a.addToSpeedX -= addToMomentumX / a.mass;
   }
 }