Initial commit

shaders/masked_palette_swap.gdshader

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+shader_type canvas_item;
+
+uniform sampler2D flag_mask : source_color, hint_default_black;
+uniform vec4 team_color : source_color = vec4(1.0, 0.0, 0.0, 1.0); // red by default
+
+void fragment() {
+    vec4 base = texture(TEXTURE, UV);
+    float mask = texture(flag_mask, UV).r; // 1.0 on flag pixels, 0.0 on castle
+
+    // Use the grey luminance as a brightness multiplier on the team color
+    float brightness = base.r; // grey means R == G == B
+    vec4 tinted = vec4(team_color.rgb * brightness * 2.0, base.a);
+
+    // Blend: castle pixels stay grey, flag pixels get tinted
+    COLOR = mix(base, tinted, mask);
+}