diff --git a/DEVELOPMENT.md b/DEVELOPMENT.md
index 933456e..4c25055 100644
--- a/DEVELOPMENT.md
+++ b/DEVELOPMENT.md
@@ -89,8 +89,8 @@ make -f Makefile.dev release-arch
   - [x] src  9 : sentences repeat h
   - [x] src 10 : isometric grid
   - [x] src 12 : pattern in my kitchen
-  - [ ] src 13 : cursor with select
-  - [ ] src 14 : ?
+  - [x] src 13 : another pattern in my kitchen
+  - [ ] src 14 : cursor with select
   - [ ] src 15 : ?
   - [x] fx 11 : spill
   - [x] fx 12 : game of life
diff --git a/README.md b/README.md
index 79fb67d..8569054 100644
--- a/README.md
+++ b/README.md
@@ -153,7 +153,7 @@ options:
 |       | **9** | Isometric grid    | _Zoom_            | _Scroll_        | _Elevation_        | Lens             | _Lens limit_    | _Lens power_  | _Pre Zoom_     |
 | **3** | **A** | Video In 2 + Thru | _Hue_             | _Saturation_    | _Light_            | Spill            | _Bottom limit_  | _Top Limit_   | _Rotation_     |
 |       | **B** | Scales            | _Zoom_            | _Shape_         | _Ripples_          | Game Of Life     | _Pixel Size_    | _Ruleset/Threshold_ | _Feedback_               |
-|       | **C** | (same as 6)       |                   |                 |                    | Sobel Filter    | _Horz. filter_   | _Vert. filter_ | _Filter Size_ |
+|       | **C** | Credenza          | _Zoom_            | _Shape_         | _Ripples_          | Sobel Filter    | _Horz. filter_   | _Vert. filter_ | _Filter Size_ |
 |       | **D** | (same as 7)       |                   |                 |                    | (same as 0)     |                  |               |                |
 |       | **E** | (same as 8)       |                   |                 |                    | (same as 1)     |                  |               |                |
 
diff --git a/default/inc_src.glsl b/default/inc_src.glsl
index f367d0b..cedf095 100644
--- a/default/inc_src.glsl
+++ b/default/inc_src.glsl
@@ -389,10 +389,9 @@ subroutine(src_stage_sub) vec4 src_12(vec2 vUV, int seed, vec3 b1, vec2 f1, vec3
     return vec4(f);
 }
 
-// TODO SRC 13
+// SRC 13 : Credenza
 subroutine(src_stage_sub) vec4 src_13(vec2 vUV, int seed, vec3 b1, vec2 f1, vec3 b2, vec2 f2, vec3 b3, vec2 f3)
 {
-    return src_7(vUV, seed, b1, f1, b2, f2, b3, f3);
     // start
 
 	vec2 uv0 = vUV.st;
@@ -401,9 +400,25 @@ subroutine(src_stage_sub) vec4 src_13(vec2 vUV, int seed, vec3 b1, vec2 f1, vec3
 
     // controls
 
+    float zoom = 5 + magic(f1, b1, seed + 10) * 15;
+    float shape = 0.1 + magic(f2, b2, seed + 20) * 0.9;
+    float repeat = 1 + magic(f3, b3, seed + 30) * 10;
+
     // logic
+
+    vec2 uv2 = uv1;
+
+    uv2 *= zoom;
     
-    return texture(iTex0, vUV);
+    uv2 = mod(uv2, 2);
+
+    uv2 = abs(uv2 - 1);
+
+    float f = istep(1, length(uv2)) * istep(1, length(1 - uv2));
+
+    f *= istep(0.5, saw((length(uv2) + shape + 0.5) * repeat)) * istep(0.5, saw((length(1 - uv2) + shape + 0.5) * repeat));
+    
+    return vec4(f);
 }
 
 // TODO SRC 14