Localize prompts and fix seat belt logic

Replace English serial messages with Polish, rename `prevUpdate` to
`prevEngineUpdate` for clearer engine timing, simplify RFID checks by
removing unused variables, and correct seat‑belt logic to reset when
distance ≥ 200 cm.

Projekt_Arduino.ino

@@ -13,7 +13,7 @@ Sonar sonar(TRIG_AND_ECHO_PIN, SONAR_MAX_DIST_CM);
 RFIDReader rfid(SS_PIN, RST_PIN);
 Engine engine(THROTTLE_PIN, CLUTCH_PIN, BRAKE_PIN);
 
-unsigned long prevUpdate = 0;
+unsigned long prevEngineUpdate = 0;
 bool carEnabled = false;
 unsigned long prevSonarUpdate = 0;
 bool seatBelts = false;
@@ -21,18 +21,18 @@ bool seatBelts = false;
 void setup() {
   Serial.begin(9600);
 
-  Serial.println(F("Enter car mass in kg (e.g. 1200):"));
+  Serial.println(F("Podaj wagę samochodu w kg (np. 1200):"));
   while (true) {
     if (Serial.available() > 0) {
       float mass = Serial.parseFloat();
       if (mass > 0) {
         engine.setCarMass(mass);
-        Serial.print(F("Car mass set to "));
+        Serial.print(F("Waga samochodu ustawiona na: "));
         Serial.print(mass);
         Serial.println(F(" kg"));
         break;
       } else {
-        Serial.println(F("Invalid value – try again:"));
+        Serial.println(F("Niepoprawna wartość, spróbuj ponownie:"));
       }
     }
   }
@@ -50,11 +50,6 @@ void setup() {
 }
 
 void loop() {
-  bool check = rfid.check();
-  bool matches = rfid.matches(AUTH_UID, AUTH_UID_SIZE);
-
-  bool rfidOk = check && matches;
-
   if (rfid.check() && rfid.matches(AUTH_UID, AUTH_UID_SIZE)) {
     carEnabled = !carEnabled;
 
@@ -71,22 +66,23 @@ void loop() {
       display.updateGear(gear.getGearChar());
 
     unsigned long now = millis();
-    float dt = (now - prevUpdate) / 1000.0f;
+    float dt = (now - prevEngineUpdate) / 1000.0f;
     if (dt >= 0.02f) {
-      prevUpdate = now;
+      prevEngineUpdate = now;
       engine.update(dt, gear.getGear());
       display.updateRPM(engine.getRPM());
       display.updateSpeed(engine.getSpeedKmh());
     }
 
-    if (millis() - prevSonarUpdate >= 100) {
+    unsigned long now = millis();
-      prevSonarUpdate = millis();
+    if (now - prevSonarUpdate >= 100) {
+      prevSonarUpdate = now;
       long dist = sonar.measure();
       if (!seatBelts) {
         if (dist < 200) seatBelts = true;
       }
       else {
-        if (dist >= 200) seatBelts = true;
+        if (dist >= 200) seatBelts = false;
       }
     }
   }