diff --git a/main.c b/main.c
index 8c19336..7f35a17 100644
--- a/main.c
+++ b/main.c
@@ -35,8 +35,10 @@
 #include "usb_cdcacm.h" // USB CDC ACM utilities
 #include "led_ws2812b.h" // WS2812b LEDs utilities
 
-/* flag set in interrupts to be processed in main taks */
-volatile bool button_flag = false; // button has been presse
+/* flag set in interrupts to be processed in main task */
+volatile bool button_flag = false; // button has been pressed
+
+uint8_t clock_leds[WS2812B_LEDS*3] = {0}; // RGB values for the WS2812b clock LEDs
 
 /* default output (i.e. for printf) */
 int _write(int file, char *ptr, int len)
@@ -84,6 +86,34 @@ void led_toggle(void)
 	gpio_toggle(LED_PORT, LED_PIN);
 }
 
+/* switch off all clock LEDs */
+static void leds_clear(void)
+{
+	// set all colors of all LEDs to 0
+	for (uint16_t i=0; i<LENGTH(clock_leds); i++) {
+		clock_leds[i] = 0;
+	}
+}
+
+/* set hours mark on clock LEDs */
+static void leds_hours(void)
+{
+	for (uint8_t hour=0; hour<12; hour++) {
+		uint16_t led = LENGTH(clock_leds)/3/12*hour;
+		clock_leds[led*3+0] = 0xff;
+		clock_leds[led*3+1] = 0xff;
+		clock_leds[led*3+2] = 0xff;
+	}
+}
+
+/* set the LEDs */
+static void leds_set(void)
+{
+	for (uint16_t i=0; i<LENGTH(clock_leds)/3; i++) {
+		ws2812b_set_rgb(i,clock_leds[i*3+0],clock_leds[i*3+1],clock_leds[i*3+2]);
+	}
+}
+
 int main(void)
 {	
 	SCB_VTOR = (uint32_t) 0x08002000; // relocate vector table because of the bootloader
@@ -111,6 +141,7 @@ int main(void)
 #endif
 
 	ws2812b_setup(); // setup WS2812b LEDs
+	leds_clear(); // clear LED values
 
 	printf("welcome to the CuVoodoo LED clock\n"); // print welcome message
 	led_on(); // switch on LED to indicate setup completed
@@ -139,18 +170,28 @@ int main(void)
 			printf("%c",c); // echo receive character
 			switch (c) {
 				case 'r': // set red color
-					ws2812b_set_rgb(0,0xff,0,0);
+					clock_leds[0] = 0xff;
+					clock_leds[1] = 0;
+					clock_leds[2] = 0;
 					break;
 				case 'g': // set green color
-					ws2812b_set_rgb(0,0,0xff,0);
+					clock_leds[0] = 0;
+					clock_leds[1] = 0xff;
+					clock_leds[2] = 0;
 					break;
 				case 'b': // set blue color
-					ws2812b_set_rgb(0,0,0,0xff);
+					clock_leds[0] = 0;
+					clock_leds[1] = 0;
+					clock_leds[2] = 0xff;
+					break;
+				case 'h': // show hours
+					leds_hours();
 					break;
 				default: // set no color
-					ws2812b_set_rgb(0,0,0,0);
+					leds_clear();
 					break;
 			}
+			leds_set(); // set the colors of all LEDs
 			ws2812b_transmit(); // transmit set color
 		}
 		while (button_flag) {