Shader "DashGame/Timer"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}

		[Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip("Use Alpha Clip", Float) = 0
	}

	SubShader
	{
		Tags
		{
			"Queue" = "Transparent"
			"RenderType" = "Transparent"
			"PreviewType" = "Plane"
			"IgnoreProjector" = "True"
			"CanUseSpriteAtlas" = "True"
		}

		Lighting Off
		Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag

			#include "UnityUI.cginc"
			#include "UnityCG.cginc"

			struct appdata
			{
				float2 uv : TEXCOORD0;
				float4 color : COLOR;
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 color : COLOR;
				float4 vertex : SV_POSITION;
			};

			float _Fill;
			float4 _MainTex_ST;
			sampler2D _MainTex;
			
			v2f vert (appdata v)
			{
				v2f o;

				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				o.color = v.color;
				o.vertex = UnityObjectToClipPos(v.vertex);

				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				fixed4 col = tex2D(_MainTex, i.uv);
				
				col.a *= i.color.a;

				float angleF;
				float angleR;

				if(_Fill>=1)
				{
					col.a=0;
				}
				else
				{
					if(i.uv.x <= 0.5 && i.uv.y >= 0.5)
					{
						float x = 0.5-i.uv.x;
						float y = i.uv.y - 0.5;

					 	angleR = degrees(atan(x/y));
					}
					else if(i.uv.x <= 0.5 && i.uv.y <= 0.5)
					{
						float x = 0.5-i.uv.x;
						float y = 0.5-i.uv.y;

					 	angleR = 90 + degrees(atan(y/x));
					}
					else if(i.uv.x >= 0.5 && i.uv.y <= 0.5)
					{
						float x = i.uv.x-0.5;
						float y = 0.5-i.uv.y;

					 	angleR = 180 + degrees(atan(x/y));
					}
					else if(i.uv.x >= 0.5 && i.uv.y >= 0.5)
					{
						float x = i.uv.x-0.5;
						float y = i.uv.y-0.5;

					 	angleR = 270 + degrees(atan(y/x));
					}

					angleF = 360*_Fill;

					float angleOffset = angleF - angleR;

					if(angleOffset > 45)
					{
						col.a*=1-(angleOffset-45)/45;
					}
					else if (angleOffset < 0)
					{
						col.a = 0;
					}
				}

				return col;
			}
			ENDCG
		}
	}
}