diff --git a/firmware/apps/blinker.c b/firmware/apps/blinker.c
index fc45329..f2b9012 100644
--- a/firmware/apps/blinker.c
+++ b/firmware/apps/blinker.c
@@ -3,14 +3,29 @@
 #include <pentabug/app.h>
 #include <pentabug/hal.h>
 
+#ifdef MATRIX
+uint8_t inv = 0;
+#endif
+
 static void init(void) {
 	led_on(RIGHT);
+	matrix_start();
 }
 
 static void blinker(void) {
 	led_inv(RIGHT);
 	led_inv(LEFT);
 
+#ifdef MATRIX
+	for(uint8_t x = 0; x < 3; ++x) {
+		for(uint8_t y = 0; y < 3; ++y) {
+			matrix_set(x, y, ((x + y) & 1) ^ inv);
+		}
+	}
+
+	inv = !inv;
+#endif
+
 	wait_ms(500);
 
 	if(button_clicked(RIGHT)) {
diff --git a/firmware/lib/matrix.c b/firmware/lib/matrix.c
index 35826c8..8cea181 100644
--- a/firmware/lib/matrix.c
+++ b/firmware/lib/matrix.c
@@ -13,24 +13,24 @@ void matrix_init(void) {
 }
 
 static void move_line(uint8_t line) {
-	PORTD &= ~0xe0;
-	PORTD |= 1 << (line + 5);
+	PORTD |= 0xe0;
+	PORTD &= ~(1 << (line + 5));
 }
 
 static void write_line(uint8_t data[]) {
-	PORTC |= (1 << 5) | (1 << 4);
-	PORTB |= 1 << 2;
+	PORTC &= ~((1 << 5) | (1 << 4));
+	PORTB &= ~(1 << 2);
 
 	if(data[0]) {
-		PORTC &= ~(1 << 5);
+		PORTC |= 1 << 5;
 	}
 
 	if(data[1]) {
-		PORTC &= ~(1 << 4);
+		PORTC |= 1 << 4;
 	}
 
 	if(data[2]) {
-		PORTB &= ~(1 << 2);
+		PORTB |= 1 << 2;
 	}
 }