message: Simplified opacity prop
diff: @@ -8,9 +8,9 @@ export default ({stateNavigator}) => (
  startStateKey="grid"
  unmountedStyle={{opacity: 0}}
  mountedStyle={{opacity: 1}}
  - crumbStyle={{opacity: .9}}
  + crumbStyle={{opacity: 0}}
  style={{flex: 1}}
  - sharedElementMotion={(props) => <ZoomShared {...props} />}
  + sharedElementMotion={props => <ZoomShared {...props} />}
  stateNavigator={stateNavigator}>
  {({opacity}, scene, url) => (
  <View key={url}
  @@ -20,7 +20,7 @@ export default ({stateNavigator}) => (
  right: 0,
  top: 0,
  bottom: 0,
  - opacity: opacity === 1 ? opacity : opacity / 2
  + opacity
  }}>
  {scene}
  </View>
  