diff --git a/beep/main.c b/beep/main.c
index 859f996..05a1872 100644
--- a/beep/main.c
+++ b/beep/main.c
@@ -1,21 +1,51 @@
+/*
+ * Control PB5 with the two buttons. One button disables, the other enables.
+ * The board uses interrupts for this. PB5 will quickly oscilate between on and
+ * off to make cool sounds with a summer.
+ */
 #define F_CPU 16000000UL
 #define __AVR_ATmega328P__
+#include <util/delay.h>
+#include <avr/interrupt.h>
 #include <avr/io.h>
 
-int main(void) {
-  DDRB = 0xff;
-  DDRD = 0;
+int beep = 0;
+int sound = 0;
 
-  PORTD |= (1 << PORTD2) | (1 << PORTD3);
+// code for INT0
+ISR(INT0_vect) { beep = 1; }
+
+// code for INT1
+ISR(INT1_vect) { beep = 0; PORTB &= ~(1 << PORTB5); sound = 0;}
+
+int main(void) {
+
+  DDRB = 0xff; // write to B
+  DDRD = 0;    // read from D
+
+  PORTD |= (1 << PORTD2) | (1 << PORTD3); // pull up D2 and D3
 
   PORTB = 0;
 
+  // enable external interruprs
+  EIMSK |= (1 << INT0);
+  EIMSK |= (1 << INT1);
+
+  // trigger when anything changes
+  EICRA |= (1 << ISC00); // for INT0
+  EICRA |= (1 << ISC10); // for INT1
+
+  sei(); // interrupt magic macro
   while (1) {
-    if (!(PIND & (1 << PIND2))) {
+    if (beep) {
       PORTB |= (1 << PORTB5);
-    }
-    if (!(PIND & (1 << PIND3))) {
+      _delay_us(sound);
       PORTB &= ~(1 << PORTB5);
+      _delay_us(sound);
+      sound++;
+      if (sound > 1000) {
+        sound = 0;
+      }
     }
   }
 }