diff --git a/drm/shadertoy.c b/drm/shadertoy.c
index eb216e7..b34b60c 100644
--- a/drm/shadertoy.c
+++ b/drm/shadertoy.c
@@ -357,6 +357,8 @@ int indirect_buffer()
   // VAP_PVS
   //////////////////////////////////////////////////////////////////////////////
 
+  // vertex constants
+
   T0V(VAP_PVS_CONST_CNTL
       , VAP_PVS_CONST_CNTL__PVS_CONST_BASE_OFFSET(0)
       | VAP_PVS_CONST_CNTL__PVS_MAX_CONST_ADDR(1)
@@ -366,13 +368,15 @@ int indirect_buffer()
       , VAP_PVS_VECTOR_INDX_REG__OCTWORD_OFFSET(1024)
       );
 
-  const float consts[] = {
+  const float vertex_consts[] = {
     4.0f / 3.0f, 0.0f, 0.0f, 0.0f,
   };
-  int consts_length = (sizeof (consts)) / (sizeof (consts[0]));
-  T0_ONE_REG(VAP_PVS_VECTOR_DATA_REG_128, (consts_length - 1));
-  for (int i = 0; i < consts_length; i++)
-    ib[ix++].f32 = consts[i];
+  int vertex_consts_length = (sizeof (vertex_consts)) / (sizeof (vertex_consts[0]));
+  T0_ONE_REG(VAP_PVS_VECTOR_DATA_REG_128, (vertex_consts_length - 1));
+  for (int i = 0; i < vertex_consts_length; i++)
+    ib[ix++].f32 = vertex_consts[i];
+
+  // vertex code
 
   T0V(VAP_PVS_CODE_CNTL_0
       , VAP_PVS_CODE_CNTL_0__PVS_FIRST_INST(0)
@@ -430,8 +434,25 @@ int indirect_buffer()
   // GA_US
   //////////////////////////////////////////////////////////////////////////////
 
+  // fragment constants
+
+  const float fragment_consts[] = {
+    -0.1f, 0, 0, 0,
+  };
+  int fragment_consts_length = (sizeof (fragment_consts)) / (sizeof (fragment_consts[0]));
+
+  T0V(GA_US_VECTOR_INDEX
+      , GA_US_VECTOR_INDEX__INDEX(0)
+      | GA_US_VECTOR_INDEX__TYPE(1)
+      );
+  T0_ONE_REG(GA_US_VECTOR_DATA, (fragment_consts_length - 1));
+  for (int i = 0; i < fragment_consts_length; i++)
+    ib[ix++].f32 = fragment_consts[i];
+
+  // fragment code
+
   const uint32_t fragment_shader[] = {
-    #include "shadertoy.fs.inc"
+    #include "shadertoy_circle.fs.inc"
   };
   const int fragment_shader_length = (sizeof (fragment_shader)) / (sizeof (fragment_shader[0]));
   assert(fragment_shader_length % 6 == 0);
@@ -455,7 +476,10 @@ int indirect_buffer()
       | US_CODE_ADDR__END_ADDR(fragment_shader_instructions - 1)
       );
 
-  T0V(GA_US_VECTOR_INDEX, 0x00000000);
+  T0V(GA_US_VECTOR_INDEX
+      , GA_US_VECTOR_INDEX__INDEX(0)
+      | GA_US_VECTOR_INDEX__TYPE(0)
+      );
   T0_ONE_REG(GA_US_VECTOR_DATA, fragment_shader_length - 1);
   for (int i = 0; i < fragment_shader_length; i++) {
     ib[ix++].u32 = fragment_shader[i];
diff --git a/drm/shadertoy_circle.fs.asm b/drm/shadertoy_circle.fs.asm
new file mode 100644
index 0000000..7fb3dcb
--- /dev/null
+++ b/drm/shadertoy_circle.fs.asm
@@ -0,0 +1,29 @@
+# CONSTS[0] = (-0.1, 0, 0, 0)
+
+# d = length(uv)
+src0.rgb = temp[0]  :
+  temp[0].r    = DP3 src0.rg0 src0.rg0 ;
+src0.rgb = temp[0]  :
+  temp[0].a    = RSQ |src0.r| ;
+src0.a   = temp[0]  :
+  temp[0].a    = RCP src0.a ;
+
+# d -= 0.5
+src0.a   = temp[0]  :
+  temp[0].r    = MAD src0.a00 src0.100 -src0.h00 ;
+
+# d = abs(d) * 1 + -0.1
+src0.rgb = temp[0] , src1.rgb = const[0] :
+  temp[0].r    = MAD |src0.r00| src0.100 src1.r00 ;
+
+# out.r = (d >= 0.0) ? 1.0 : 0.0
+OUT
+src0.rgb = temp[0]  :
+  out[0].r    = CMP src0.100 src0.000 src0.r00 ;
+
+# out.a = 1
+# out.gb = vec2(0, 0)
+OUT TEX_SEM_WAIT
+ :
+  out[0].a    = MAX src0.1 src0.1 ,
+  out[0].gb   = MAX src0.000 src0.000 ;
diff --git a/drm/shadertoy_circle.fs.inc b/drm/shadertoy_circle.fs.inc
new file mode 100644
index 0000000..9e28b79
--- /dev/null
+++ b/drm/shadertoy_circle.fs.inc
@@ -0,0 +1,49 @@
+0x00000800,
+0x08020000,
+0x08020080,
+0x00840420,
+0x00000000,
+0x00000001,
+
+0x00004000,
+0x08020000,
+0x08020080,
+0x00000000,
+0x0004000b,
+0x00000000,
+
+0x00004000,
+0x08020080,
+0x08020000,
+0x00000000,
+0x0000c00a,
+0x00000000,
+
+0x00000800,
+0x08020080,
+0x08020000,
+0x0093048c,
+0x00000000,
+0x00c94000,
+
+0x00000800,
+0x08040000,
+0x08020080,
+0x00931480,
+0x00000000,
+0x00481000,
+
+0x00008001,
+0x08020000,
+0x08020080,
+0x00920498,
+0x00000000,
+0x00480008,
+
+0x00070005,
+0x08020080,
+0x08020080,
+0x00920490,
+0x00c18003,
+0x00000005,
+
diff --git a/shader_examples/mesa/shadertoy_circle.fs.txt b/shader_examples/mesa/shadertoy_circle.fs.txt
new file mode 100644
index 0000000..487aab5
--- /dev/null
+++ b/shader_examples/mesa/shadertoy_circle.fs.txt
@@ -0,0 +1,48 @@
+0x00000800,
+0x08020000,
+0x08020080,
+0x00840420,
+0x00000000,
+0x00000001,
+
+0x00004000,
+0x08020000,
+0x08020080,
+0x00000000,
+0x0004000b,
+0x00000000,
+
+0x00004000,
+0x08020080,
+0x08020000,
+0x00000000,
+0x0000c00a,
+0x00000000,
+
+0x00000800,
+0x08020080,
+0x08020000,
+0x0093048c,
+0x00000000,
+0x00c94000,
+
+0x00000800,
+0x08040000,
+0x08020080,
+0x00931480,
+0x00000000,
+0x00481000,
+
+0x00008001,
+0x08020000,
+0x08020080,
+0x1c920498,
+0x00000000,
+0x00480008,
+
+0x00070005,
+0x08020080,
+0x08020080,
+0x1c920490,
+0x1cc18003,
+0x00000005,