For @Tomeno; Shader form of Cooldown Animation (#1113)

Co-authored-by: Tomeno <tomeno@lulzsec.co.uk>

Resources/Prototypes/Shaders/cooldown.yml

@@ -0,0 +1,6 @@
+- type: shader
+  id: CooldownAnimation
+  kind: source
+  path: "/Shaders/cooldown.swsl"
+  params:
+    progress: 0

Resources/Shaders/cooldown.swsl

@@ -0,0 +1,25 @@
+light_mode unshaded;
+
+const float PI = 3.14159265;
+
+uniform float progress = 0.0;
+
+void fragment() {
+    vec4 col = texture(TEXTURE, UV);
+    vec2 center = vec2(0.5,0.5);
+    vec2 delta = UV.xy - center;
+    
+    float angle = atan(delta.x, -delta.y) + PI;
+
+    float dist = length(delta);
+    float dist_fwidth = fwidth(dist) * 0.67;
+    
+    float dist_alpha = smoothstep(0.1-dist_fwidth, 0.1, abs(dist-0.35));
+    
+    float angle_delta = (progress * PI * 2) - angle;
+    float arc_length = angle_delta * dist;
+    
+    float angle_alpha = progress > 0 ? smoothstep(dist_fwidth, 0.0, arc_length) : 0.0;
+
+    COLOR = vec4(col.xyz, 1-max(dist_alpha, angle_alpha));
+}