Replace delay() with ISR_Timer

button.ino

@@ -1,11 +1,22 @@
 volatile unsigned long lastButtonPress = millis();
 
+void initButton() {
+  pinMode(BUTTON_PIN, INPUT_PULLUP);
+  // Order of ISRs matter: RISING should be invoked first
+  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), buttonISRtime, CHANGE);
+  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), buttonISRstate, RISING);  
+}
+
 void buttonISRstate() {
   if ((millis() - lastButtonPress) > 100) {
-    if (countdown > 0)
+    if (countdown < 0)
       countdown = 0;
-    else
-      countdown = BREAK_LENGTH;
+    else if (countdown == 0)
+      countdown = COUNTDOWN;
+    else {
+      countdown = -1;
+      digitalWrite(BUTTON_LED_PIN, LOW);
+    }
   }
 }