const int incrPin = 2;
const int decrPin = 4;
const int ledPin = 13;

int ledState = LOW;
int changeSpd = 500;
int changeStep = 0;
int prevTime = 0;

int incrButtonState;
int decrButtonState;

int lastIncrButtonState = LOW;
int lastDecrButtonState = LOW;

unsigned long lastIncrDebounceTime = 0;
unsigned long lastDecrDebounceTime = 0;
unsigned long debounceDelay = 50;

void setup() {
        Serial.begin(9600);
        Serial.println("init");

        prevTime = millis();

    pinMode(incrPin, INPUT);
    pinMode(decrPin, INPUT);
    pinMode(ledPin, OUTPUT);

    digitalWrite(ledPin, ledState);
}

void loop() {
    int incrState = digitalRead(incrPin);
    int decrState = digitalRead(decrPin);

    if (incrState != lastIncrButtonState) {
        lastIncrDebounceTime = millis();
    }
    if (decrState != lastDecrButtonState) {
        lastDecrDebounceTime = millis();
    }

        //Serial.println("Current " + String(incrState) + ", Last: " + String(lastIncrButtonState));
//          Serial.println("Tick: " + String(changeStep));
Serial.println(String(changeSpd));

    if ((millis() - lastIncrDebounceTime) > debounceDelay) {
                if (incrState != incrButtonState) {
                        incrButtonState = incrState;
                if (incrState == HIGH) {
                               handleIncr();
                }
                }
    }

    if ((millis() - lastDecrDebounceTime) > debounceDelay) {
                if (decrState != decrButtonState) {
                        decrButtonState = decrState;
                if (decrState == HIGH) {
                               handleDecr();
                }
                }
    }

    lastIncrButtonState = incrState;
    lastDecrButtonState = decrState;

        //Change the light state

        changeStep += (millis() - prevTime);
        prevTime = millis();

        if (changeStep >= changeSpd) {
              ledState = (ledState == 0) ? 1 : 0;
              digitalWrite(ledPin, ledState);
              changeStep = 0;
        }
}

void handleIncr() {
        Serial.println("incr");
        changeSpd += 50;
}

void handleDecr() {
        Serial.println("decr");
        changeSpd -= 50;
}