Make car mass configurable at runtime

Replace the compile‑time CAR_MASS constant with a runtime‑settable
_member _carMass. Add Engine::setCarMass, default it to 1200 kg, and
use it in the acceleration calculation. Prompt the user for the
car mass on startup via Serial and update the enable/disable messages.

Projekt_Arduino.ino

@@ -21,6 +21,29 @@ bool seatBelts = false;
 void setup() {
   Serial.begin(9600);
 
+    // -----------------------------------------------------------------
+    // 1. Ask the user for the car mass (kg) via the Serial monitor.
+    //    We block only until a valid number is received – this is OK
+    //    because it happens once at startup.
+    // -----------------------------------------------------------------
+    Serial.println(F("Enter car mass in kg (e.g. 1200):"));
+    while (true) {
+      // Wait until something is typed
+      if (Serial.available() > 0) {
+        float mass = Serial.parseFloat();          // reads the number
+        if (mass > 0) {                            // basic sanity check
+          engine.setCarMass(mass);
+          Serial.print(F("Car mass set to "));
+          Serial.print(mass);
+          Serial.println(F(" kg"));
+          break;
+        } else {
+          Serial.println(F("Invalid value – try again:"));
+        }
+      }
+    }
+
+
   pinMode(IN_1, OUTPUT);
   pinMode(IN_2, OUTPUT);
   pinMode(ENA_1, OUTPUT);
@@ -41,8 +64,12 @@ void loop() {
 
   if (rfid.check() && rfid.matches(AUTH_UID, AUTH_UID_SIZE)) {
     carEnabled = !carEnabled;
-    Serial.print("Auto działa: ");
-    Serial.println(carEnabled);
+
+    if (carEnabled)
+      Serial.println("Uruchamiam auto");
+    else
+      Serial.println("Gaszę auto");
+
     display.startOrEnd(carEnabled);
   };