Background color doesn't get changed when I hover on btn

[netninja25253]

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Hello, it’s me again.
I’ve tried to change color of btn when I hover. (blue → white)

so I put code as below.
But it doesn’t work as I meant. It seems like some kinda force is preventing me from hustling.
Here is my code.

.btn {
  background-color: black;
  border: 1px solid black;
  color: white;
  text-decoration: none;
  padding: 10px 40px;
}

.btn:hover {
 background-color: white;
 cursor: pointer; 
 transition: background .5s;  
}

Thanks in advance again!