Shader "Custom/OutlineGlow"
{
    Properties
    {
        _MainTex("Sprite Texture", 2D) = "white" {}
        _OutlineColor("Outline Color", Color) = (1,1,0,1)  // 发光颜色
        _OutlineWidth("Outline Width", Range(0, 0.1)) = 0.02  // 外发光宽度
    }
        SubShader
        {
            Tags {"Queue" = "Transparent" "RenderType" = "Transparent"}
            Blend SrcAlpha OneMinusSrcAlpha
            Cull Off
            Lighting Off
            ZWrite Off

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

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

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

                sampler2D _MainTex;
                float4 _OutlineColor;
                float _OutlineWidth;

                v2f vert(appdata_t v) {
                    v2f o;
                    o.vertex = UnityObjectToClipPos(v.vertex);
                    o.uv = v.uv;
                    return o;
                }

                fixed4 frag(v2f i) : SV_Target {
                    float2 uv = i.uv;
                    fixed4 texColor = tex2D(_MainTex, uv);

                    // 计算外轮廓
                    float alpha = texColor.a;
                    float outlineAlpha = (
                        tex2D(_MainTex, uv + float2(_OutlineWidth, 0)).a +
                        tex2D(_MainTex, uv + float2(-_OutlineWidth, 0)).a +
                        tex2D(_MainTex, uv + float2(0, _OutlineWidth)).a +
                        tex2D(_MainTex, uv + float2(0, -_OutlineWidth)).a
                    ) * 0.25;

                    fixed4 outlineColor = _OutlineColor;
                    outlineColor.a *= outlineAlpha;  // 让外轮廓柔和一些

                    return lerp(outlineColor, texColor, alpha);
                }
                ENDCG
            }
        }
}