fix(misc): remove unused imports + fix angle computation

Author: MinaPecheux

Diff for: Assets/Editor/Build.cs

@@ -1,5 +1,4 @@
 using System.Linq;
-using System;
 using UnityEditor;
 using UnityEngine;
 

Diff for: Assets/Scripts/GameHandler.cs

@@ -41,7 +41,7 @@ public void InitializeBall(Rigidbody2D ball)
             else if (r < 0.5f)
                 angle += 180f;
             else if (r < 0.75f)
-                angle += 360f - angle;
+                angle = 360f - angle;
             float strength = 10f;
             ball.velocity = new Vector2(
                 strength * Mathf.Cos(angle),

Diff for: Assets/Tests/EditorTests/Runner.cs

@@ -1,4 +1,3 @@
-using System.Xml;
 using UnityEditor;
 using UnityEditor.TestTools.TestRunner.Api;
 using UnityEngine;