Correct

黑洞洞

/ hēidòngdòng / 
Strokes

Definition

pitch-dark

Example

As an Adjective

pitch-dark

1
Jǐng
井
hěn
很
shēn
深
  
,
hēidòngdòng
黑洞洞
de
的
  
。

The well is deep and pitch-dark.