title: React Spring Transition not working properly
body: <p>So I've looked at the react springs docs, and I'm sure I'm just not understanding it properly. But I wanted to essentially try to make a div have an <code>enter</code> animation and some kind of trigger to make it <code>leave</code></p>
  <p>I have been unsuccessful in triggering this <code>leave</code>. I can't seem to understand what makes it trigger the leave functionality. Or maybe I'm just not understanding the transition in general which is entirely possible.</p>
  <p>The idea is simple, I want to be able to trigger something to come into view, and then when something else happens, to trigger it to go out of view.</p>
  <p>I took an example from the react-spring docs, and <a href="https://codesandbox.io/s/laughing-meadow-1y69p" rel="nofollow noreferrer">made my own fork</a>, to demonstrate what I seem to be misunderstanding.</p>
  <p>If you go to this codepen, and click anywhere in the display box, you'll notice some animation happening. From my understanding, the state variable <code>isTrue</code> should be telling the transition what state to be in. So if it's false, I would assume this would trigger leave. But it doesnt leave, as you can see from the example, it stays at the <code>enter</code> rule (display being <code>block</code> and opacity being <code>1</code>).</p>
  <p>Essentially, I'd want it to come into view initially, and when i click on it, to trigger the <code>leave</code>  rule and have it animate out to display none and opacity 0.</p>
  <p>Any help is appreciated.</p>