title: How to set write rule for specific value
body: <p>I'm developing an Android app using the firebase. There is a"Score" for each user.</p>
  
  <pre><code>user:
      $uid:
       "Score":100
  </code></pre>
  
  <p>Like that.</p>
  
  <p>Only admin can read and write "Score". User can only read it. But when the user breaks rules or policies, his score will be reduced automatically. But the problem is if I set write permission to false ,score cannot be reduced. 
  I want to set a write true if the score is increased by admin and write false in the score is reduced.
   Are there some opinions about this problem?</p>