diff --git a/firmware/src/gfx_decoder.cpp b/firmware/src/gfx_decoder.cpp
index 3be7839..1e59352 100644
--- a/firmware/src/gfx_decoder.cpp
+++ b/firmware/src/gfx_decoder.cpp
@@ -56,3 +56,52 @@ int32_t gfx_decoder_handleLoop() {
   }
   return 0;
 }
+
+void gfx_decoder_setTestFrame() {
+  uint8_t buffer[ROW_COUNT * COL_COUNT] = {0};
+
+  // le boxes
+  for (int i = 0; i < 8; i++) {
+    uint8_t color = 1 << i;
+    int startX = (i % 4) * 10;
+    int startY = (i / 4) * 10;
+
+    // box with only 1<<n color
+    for (int x = startX; x < startX + 10; x++) {
+      for (int y = startY + 5; y < startY + 10; y++) {
+        buffer[y * ROW_COUNT + x] = color;
+      }
+    }
+
+    // box with 1<<n - 1 color for comparison
+    for (int x = startX; x < startX + 10; x++) {
+      for (int y = startY; y < startY + 5; y++) {
+        buffer[y * ROW_COUNT + x] = color - 1;
+      }
+    }
+  }
+
+  // full color
+  for (int x = 30; x < ROW_COUNT; x++) {
+    for (int y = 20; y < 25; y++) {
+      buffer[y * ROW_COUNT + x] = 255;
+    }
+  }
+
+  // smooth gradient - lower range
+  for (int x = 0; x < ROW_COUNT; x++) {
+    for (int y = 30; y < 35; y++) {
+      buffer[y * ROW_COUNT + x] = x;
+    }
+  }
+
+  // smooth gradient
+  float delta = 256 / (COL_COUNT);
+  for (int x = 0; x < ROW_COUNT; x++) {
+    for (int y = 35; y < 40; y++) {
+      buffer[y * ROW_COUNT + x] = (x + 1) * delta;
+    }
+  }
+
+  leds_set_framebuffer(buffer);
+}
diff --git a/firmware/src/gfx_decoder.h b/firmware/src/gfx_decoder.h
index 02389ae..aac5d8f 100644
--- a/firmware/src/gfx_decoder.h
+++ b/firmware/src/gfx_decoder.h
@@ -10,5 +10,6 @@ extern uint8_t gfxFrameBuffer[6400];
 
 int32_t gfx_decoder_loadNextFrame();
 int32_t gfx_decoder_handleLoop();
+void gfx_decoder_setTestFrame();
 
 #endif
diff --git a/firmware/src/leds.cpp b/firmware/src/leds.cpp
index 563f466..540894c 100644
--- a/firmware/src/leds.cpp
+++ b/firmware/src/leds.cpp
@@ -40,14 +40,15 @@ uint8_t brightnessPhase = 0;
 // delays in nanoseconds
 #define NS_TO_DELAY(ns) (ns / NS_PER_CYCLE / LEDS_PIO_CLKDIV)
 uint32_t brightnessPhaseDelays[COLOR_BITS] = {
-  NS_TO_DELAY(50),
-  NS_TO_DELAY(100),
-  NS_TO_DELAY(200),
-  NS_TO_DELAY(500),
-  NS_TO_DELAY(1500),
-  NS_TO_DELAY(6000),
-  NS_TO_DELAY(20000),
-  NS_TO_DELAY(60000),
+  // NOTE: 100ns seems to be the minimum that's (barely) visible
+  /*   1 */ NS_TO_DELAY(115),
+  /*   2 */ NS_TO_DELAY(130),
+  /*   4 */ NS_TO_DELAY(140),
+  /*   8 */ NS_TO_DELAY(160),
+  /*  16 */ NS_TO_DELAY(190),
+  /*  32 */ NS_TO_DELAY(500),
+  /*  64 */ NS_TO_DELAY(3200),
+  /* 128 */ NS_TO_DELAY(14000),
 };
 
 // NOTE: Alignment required to allow 4-byte reads