Shader "Custom/FlowOverlay"
{
    Properties
    {
        _BaseMap("Base Map", 2D) = "white" {}
        _FlowTex("Flow Texture", 2D) = "white" {}
        _FlowColor("Flow Color", Color) = (1,0.5,0,1)
        _FlowSpeed("Flow Speed", Float) = 1.0
        _FlowAngle("Flow Angle", Float) = 0.0
        _Tiling("Flow Tiling", Vector) = (1,1,0,0)
        _FlowStrength("Flow Strength", Float) = 1.0
    }
        SubShader
        {
            Tags { "RenderType" = "Opaque" }
            LOD 200

            Pass
            {
                CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag
                #include "UnityCG.cginc"

                sampler2D _BaseMap;
                sampler2D _FlowTex;

                float4 _FlowColor;
                float _FlowSpeed;
                float _FlowAngle;
                float4 _Tiling;
                float _FlowStrength;

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

                struct v2f
                {
                    float2 uv : TEXCOORD0;
                    float2 uvFlow : TEXCOORD1;
                    float4 vertex : SV_POSITION;
                };

                float2 RotateUV(float2 uv, float angleDeg, float2 pivot)
                {
                    float angleRad = radians(angleDeg);
                    float s = sin(angleRad);
                    float c = cos(angleRad);
                    uv -= pivot;
                    float2 rotatedUV = float2(uv.x * c - uv.y * s, uv.x * s + uv.y * c);
                    return rotatedUV + pivot;
                }

                v2f vert(appdata v)
                {
                    v2f o;
                    o.vertex = UnityObjectToClipPos(v.vertex);

                    // 原贴图UV
                    o.uv = v.uv;

                    // 电流贴图UV：先缩放，再旋转
                    float2 uvScaled = v.uv * _Tiling.xy;
                    float2 uvRotated = RotateUV(uvScaled, _FlowAngle, 0.5);
                    o.uvFlow = uvRotated + float2(_Time.y * _FlowSpeed, 0);
                    return o;
                }

                fixed4 frag(v2f i) : SV_Target
                {
                    fixed4 baseCol = tex2D(_BaseMap, i.uv);
                    fixed4 flowTex = tex2D(_FlowTex, i.uvFlow);

                    fixed4 flowColor = flowTex * _FlowColor * _FlowStrength;

                    fixed4 finalColor = baseCol + flowColor;

                    return finalColor;
                }
                ENDCG
            }
        }
}