diff --git a/lib/gfx/gx_shader.cpp b/lib/gfx/gx_shader.cpp
index 6c847a2..985382d 100644
--- a/lib/gfx/gx_shader.cpp
+++ b/lib/gfx/gx_shader.cpp
@@ -888,8 +888,15 @@ wgpu::ShaderModule build_shader(const ShaderConfig& config, const ShaderInfo& in
           var dist_attn = dot(light.dist_att, vec3f(1.0, dist, dist2));
           attn = max(0.0, cos_attn / dist_attn);)""");
       } else if (cc.attnFn == GX_AF_SPEC) {
-        diffFn = GX_DF_NONE;
-        FATAL("AF_SPEC unimplemented");
+        std::string normal = UsePerPixelLighting ? "in.mv_nrm" : "mv_nrm";
+        std::string dist_attn = diffFn != GX_DF_NONE
+                      ? "max(0.0, dot(normalize(light.dist_att), vec3f(1.0, attn, attn * attn)));"
+                      : "max(0.0, dot(light.dist_att, vec3f(1.0, attn, attn * attn)));";
+        lightAttnFn = fmt::format(R"""(
+          attn = select(0.0, max(0.0, dot({0}, light.dir)), dot({0}, ldir) >= 0.0);
+          var cos_attn = dot(light.cos_att, vec3f(1.0, attn, attn * attn));
+          var dist_attn = {1};
+          attn = max(0.0, cos_attn / dist_attn);)""", normal, dist_attn);
       }
       if (diffFn == GX_DF_NONE) {
         lightDiffFn = "1.0";