diff --git a/src/main.cpp b/src/main.cpp
index 8c53019..2dbedd7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,25 +1,42 @@
 #include "hardware/gpio.h"
 #include "pico/stdlib.h"
+#include <pico/time.h>
+
+#include <concepts>
 #include <cstdint>
 #include <cstdio>
-#include <pico/time.h>
 
 constexpr static uint start_pin = 2;
 constexpr static uint pin_mask = (0xFFF) << start_pin;
 
+template <std::integral T> constexpr bool between(T x, T min, T max) {
+  return (x >= min) && (x < max);
+}
+
 int main() {
   stdio_init_all();
 
   for (uint offset{}; offset != 14; ++offset) {
     auto const pin = start_pin + offset;
+    std::printf("Initializing GPIO %d\n", pin);
     gpio_init(pin);
     gpio_set_dir(pin, GPIO_OUT);
   }
 
-  for (uint16_t pixel{};; ++pixel) {
-    auto const set_mask = (pixel & 0xFFF) << start_pin;
-    printf("Set mask=%03x", pixel);
-    gpio_put_masked(pin_mask, set_mask);
-    sleep_ms(100);
+  for (uint32_t y{}; y != 525; ++y) {
+    for (uint32_t x{}; x != 800; ++x) {
+      const auto is_blanking = y >= 480 || x >= 640;
+      const auto hsync = between(x, 656ul, 752ul);
+      const auto vsync = between(y, 490ul, 492ul);
+
+      auto const pixel = (0u << 8) | ((y & 0xF) << 4) | (x & 0xF);
+      auto const set_mask =
+          (((uint32_t)vsync << 13) | ((uint32_t)hsync << 12) | (pixel & 0xFFF))
+          << start_pin;
+
+      std::printf("Set mask=%04X\n", set_mask >> start_pin);
+      gpio_put_masked(pin_mask, set_mask);
+      sleep_ms(10);
+    }
   }
 }