What is the 平仄 rule in 無情對 I am fascinated by 無情對,
It is two of my attempts:

四川特產北菇 (Sichuan specialty mushroom)
三洋通用東芝 (Sanyo, GM, Toshiba)

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今朝書店晚開 (Bookstore open late today)
現代本田日產 (Hyundai, Honda, Nissan)

(All in Cantonese)
I think my matching of characters is acceptable, but not sure if they fit the 平仄 rule.
My question is as follows : What is the 平仄 rule in 無情對? Does my samples correctly followed this rule?
Since you just ask for tone pattern rule, the tone pattern of couplet also matches with the poetry. So I use tone pattern of middle Chinese for reference:

This is an ideal situation:


  国破山河在，
  仄仄平平仄
  
  城春草木深。
   平平仄仄平


But sometimes it's hard to match a pair of word in level (平) tones and oblique (仄) tones, so when it comes to normal couplet case, we just require the tone of last characters must match the tones. 


  上联：雄黄酒    平平仄 
  
  下联：牡丹烟    仄平平