閉門(mén)造車(chē)

- shut oneself up in a room making a cart; carry out one's idea irrespective of external circumstances; divorce oneself from the masses and from reality and act blindly; do whatever one likes individually，oblivious of the world; draw up plans behind closed doors; indulge in fantasy (to build air castles); make a cart behind closed doors;work behind closed doors;work on [at] some project without reference to what the world requires [needs]