init commit

engine/engine.h

@@ -0,0 +1,22 @@
+#pragma once
+
+// Crankshaft rotational dynamics. Placeholder physics for now —
+// real combustion/friction torque modeling comes later.
+class Engine {
+public:
+    // load_torque_nm is the resistance fed back from the transmission
+    // (via the vehicle), opposing crank rotation.
+    void step(double dt, double load_torque_nm);
+
+    double rpm() const;
+    double torque_nm() const; // net torque produced this step
+
+    void reset();
+
+private:
+    double m_rpm = 0.0;
+    double m_torque_nm = 0.0;
+
+    static constexpr double kIdleRpm = 900.0;
+    static constexpr double kCrankInertiaKgm2 = 0.15; // placeholder
+};