AQI: scaled the circular air quality gradient to make it look nicer.

1Weather/Model/ModelObjects/Health/Health.swift

@@ -17,11 +17,19 @@ public struct Health: Equatable, Hashable {
 public struct AirQuality: Equatable, Hashable {
     public let index: Double
     public let advice: String //TODO: support for localization
-    public var progress:CGFloat {
-        var progressValue = max(0, CGFloat(index / 500))
+    public let progress: CGFloat
+    
+    public init(index: Double, advice: String) {
+        self.index = index
+        self.advice = advice
+        
+        var progressValue = CGFloat(sqrt(0.1 + (index * 0.9) / 400)) // just to make it look nicer, so that we didn't have too short gradient circle in areas with generally good air.
+            
+        progressValue = max(0, progressValue)
         progressValue = min(1, progressValue)
-        return progressValue
+        self.progress = progressValue
     }
+    
     public var status: HealthStatus {
         switch index {
         case 0...50: return .good