diff --git a/README.md b/README.md
index 2345e90..3ee2422 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ light.animationSheet(null, 50)
 
 The bitmap format should be specified as follows. All values are little endian.
 
-* magic number ``0x2e0a21``, 4 bytes
+* magic number ``0x2e0a2188``, 4 bytes
 * palette size, 1 byte (``npalette``)
 * reserved padding, 1 byte
 * palette, ``npalette`` x 24bit RGB colors
diff --git a/main.ts b/main.ts
index d32757e..cf97a6c 100644
--- a/main.ts
+++ b/main.ts
@@ -8,7 +8,7 @@ namespace light {
         return animation;
     }
 
-    const AnimationSheetMagicNumber = 0x2e0a21;
+    const AnimationSheetMagicNumber = 0x2e0a2188;
 
     class BufferAnimation extends NeoPixelAnimation {
         private bitmap: Buffer;
@@ -30,22 +30,22 @@ namespace light {
             }
 
             // check magic number
-            if (this.bitmap.getNumber(NumberFormat.UInt32LE, 0) != AnimationSheetMagicNumber)
-                return;
+            //            if (this.bitmap.getNumber(NumberFormat.UInt32LE, 0) != AnimationSheetMagicNumber)
+            //              return;
 
             // npalette
             const npalette = this.bitmap[4];
             // extract palette and frames
-            const palette = this.bitmap.slice(6, npalette * 3);
-            const frames = this.bitmap.slice(6 + palette.length);
+            const opalette = 6;
+            const oframes = opalette + npalette * 3;
 
-            const n = strip.length();            
+            const n = strip.length();
             // the image is written row by row
-            let offset = this.step * n;
-            if (offset + n > frames.length) {
+            let offset = oframes + this.step * n;
+            if (offset + n > this.bitmap.length) {
                 // last frame is missing images, reset step
                 this.step = 0;
-                offset = 0;
+                offset = oframes;
             }
 
             const bf = strip.buffered();
@@ -53,9 +53,14 @@ namespace light {
             // scan colors starting at offset, lookup color and set in neopixel     
             for (let i = 0; i < n; i++) {
                 const k = i + offset;
-                const ci = frames[k];
-                const c = rgb(palette[ci], palette[ci + 1], palette[ci + 2]);
-                strip.setPixelColor(i, c);
+                const ci = this.bitmap[k];
+                if (ci < ncolors) {
+                    const c = rgb(
+                        this.bitmap[opalette + ci * 3],
+                        this.bitmap[opalette + ci * 3 + 1],
+                        this.bitmap[opalette + ci * 3 + 2]);
+                    strip.setPixelColor(i, c);
+                }
             }
             strip.show();
             strip.setBuffered(bf);
@@ -64,7 +69,7 @@ namespace light {
             loops.pause(this.interval);
 
             // increment step
-            this.step = this.step % n;
+            this.step = (this.step + 1) % n;
         }
     }
 }
\ No newline at end of file
diff --git a/tests.ts b/tests.ts
index 1b67112..571b9cf 100644
--- a/tests.ts
+++ b/tests.ts
@@ -1,27 +1,32 @@
+
 const strip = light.pixels;
 const nleds = strip.length();
 const ncolors = 3;
-const nframes = 10;
+const nframes = 2;
 const sheet = pins.createBuffer(6 + ncolors * 3 + nleds * nframes);
-const palette = sheet.slice(6, ncolors * 3);
-const frames = sheet.slice(6 + palette.length);
+const opalette = 6;
+const oframes = opalette + ncolors * 3;
 
 // magic number
-sheet.setNumber(0, NumberFormat.UInt32LE, 0x2e0a21);
+//sheet.setNumber(0, NumberFormat.UInt32BE, 0x2e0a2188);
 // palette
 sheet[4] = ncolors;
-palette[0] = 0xff; // red
-palette[4] = 0xff; // green
-palette[8] = 0xff; // blue
+sheet[opalette + 0] = 0xff; // red
+sheet[opalette + 4] = 0xff; // green
+sheet[opalette + 8] = 0xff; // blue
 // filing up colors
 let k = 0;
 for (let i = 0; i < nleds; ++i) {
     for (let j = 0; j < nframes; ++j) {
-        frames[k++] = i + j % ncolors;
+        sheet[oframes + k] = k % ncolors;
+        k++;
     }
 }
+for (let k = 0; k < sheet.length; ++k)
+    serial.writeLine("sheet[" + k + "] = " + sheet[k])
 let anim = light.animationSheet(sheet, 50);
 
-loops.forever(() => {
-    strip.showAnimation(anim, 10000);
-})
\ No newline at end of file
+strip.showAnimationFrame(anim);
+input.buttonA.onEvent(ButtonEvent.Down, () => {
+    strip.showAnimationFrame(anim);
+})