The Subjunctive Mood(假設語氣)

Conditional

• real conditions

In the future => if-clause: simple present (#will as synonym of want), result clause: future/imperative

In the past =>  if-clause: past, result clause: past

• unreal conditions

In the present=>if-clause: past /were, result clause: would/could + simple

In the past      =>if-clause: past perfect , result clause:  would/could + have + past participle