code: function () {
          this.update = {
              velocity: function (entity, dt) {
                  entity.c.position.x += hitagi.utils.delta(entity.c.velocity.xspeed, dt);
              }
          };
      }
docs: We need to update horizontal and vertical velocity seperately for our collision resolution technique. The default hitagi VelocitySystem doesn't support this, but it's easy to make our own.