Code snippet 20 - For multiplayer space invaders article

server.js

function startMovingPhysicsWorld() {
  let p2WorldInterval = setInterval(function () {
    if (!gameOn) {
      clearInterval(p2WorldInterval);
    } else {
      // updates velocity every 5 seconds
      if (++shipVelocityTimer >= 80) {
        shipVelocityTimer = 0;
        shipBody.velocity[0] = calcRandomVelocity();
      }
      world.step(P2_WORLD_TIME_STEP);
      if (shipBody.position[0] > 1400 && shipBody.velocity[0] > 0) {
        shipBody.position[0] = 0;
      } else if (shipBody.position[0] < 0 && shipBody.velocity[0] < 0) {
        shipBody.position[0] = 1400;
      }
    }
  }, 1000 * P2_WORLD_TIME_STEP);
}