Update Project

Assets/Scripts/Gameplay/Bird/BirdController.cs

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+using UnityEngine;
+namespace FlappyBird.Gameplay.Bird
+{
+    /// <summary>
+    /// Pure C# service — all bird physics and rotation logic lives here.
+    /// No MonoBehaviour, no Unity lifecycle. Injected via Zenject.
+    /// </summary>
+    public sealed class BirdController : IBirdController
+    {
+        // ── Dependencies ────────────────────────────────────────────────────
+        private readonly Rigidbody2D _rigidbody;
+        private readonly BirdSettings _settings;
+        /// <summary>
+        /// Constructor injection (Zenject will call this).
+        /// </summary>
+        /// <param name="rigidbody">The bird's Rigidbody2D component.</param>
+        /// <param name="settings">Configurable physics parameters.</param>
+        public BirdController(Rigidbody2D rigidbody, BirdSettings settings)
+        {
+            _rigidbody = rigidbody;
+            _settings  = settings;
+
+            // Lock X position so the bird never drifts horizontally.
+            // The illusion of forward movement comes from pipes scrolling left.
+            _rigidbody.constraints = RigidbodyConstraints2D.FreezePositionX;
+        }
+        // ── IBirdController ─────────────────────────────────────────────────
+        /// <inheritdoc/>
+        public void Tick()
+        {
+            ApplyRotation();
+        }
+        /// <inheritdoc/>
+        public void Jump()
+        {
+            // Reset vertical velocity so each tap feels consistent regardless of fall speed.
+            // X is frozen via constraints, but we explicitly keep it zero for safety.
+            _rigidbody.linearVelocity = Vector2.zero;
+            _rigidbody.AddForce(Vector2.up * _settings.JumpForce, ForceMode2D.Impulse);
+        }
+        // ── Private helpers ─────────────────────────────────────────────────
+        /// <summary>
+        /// Maps vertical velocity to a tilt angle and smoothly rotates the bird.
+        /// Velocity range [rotationUpVelocity .. rotationDownVelocity] maps to
+        /// [maxUpRotation .. maxDownRotation] via an inverse-lerp → lerp.
+        /// </summary>
+        private void ApplyRotation()
+        {
+            float velocityY = _rigidbody.linearVelocity.y;
+            // Normalise velocity to [0, 1] (0 = falling fast, 1 = rising fast).
+            float t = Mathf.InverseLerp(
+                _settings.RotationDownVelocity,
+                _settings.RotationUpVelocity,
+                velocityY);
+            float targetAngle = Mathf.Lerp(
+                _settings.MaxDownRotation,
+                _settings.MaxUpRotation,
+                t);
+            // Read current Z rotation from the transform via the rigidbody.
+            float currentAngle = _rigidbody.rotation;
+            float smoothedAngle = Mathf.LerpAngle(
+                currentAngle,
+                targetAngle,
+                _settings.RotationSpeed * Time.deltaTime);
+            _rigidbody.MoveRotation(smoothedAngle);
+        }
+    }
+}