diff --git a/config/performance.yaml b/config/performance.yaml
new file mode 100644
index 0000000..83cf1b6
--- /dev/null
+++ b/config/performance.yaml
@@ -0,0 +1,20 @@
+performance:
+  target_fps: 60
+  asset_cache_limit_mb: 200
+  scene_cache_mode: "on_demand"
+  diagnostics_enabled: true
+  unload_idle_scenes: true
+
+profiles:
+  balanced:
+    target_fps: 60
+    cache_limit: 200
+    diagnostics: true
+  low_power:
+    target_fps: 30
+    cache_limit: 100
+    diagnostics: false
+  max_quality:
+    target_fps: 120
+    cache_limit: 400
+    diagnostics: false
diff --git a/engine/performance_manager.py b/engine/performance_manager.py
new file mode 100644
index 0000000..f64a39c
--- /dev/null
+++ b/engine/performance_manager.py
@@ -0,0 +1,115 @@
+from __future__ import annotations
+
+import logging
+import os
+import sys
+from typing import List, Dict, Optional
+
+try:  # pragma: no cover - allow running tests without pygame
+    import pygame
+except Exception:  # pragma: no cover - allow running tests without pygame
+    pygame = None
+
+try:
+    import yaml
+except Exception:  # pragma: no cover - allow running tests without PyYAML
+    yaml = None
+
+from .asset_manager import AssetManager
+
+logger = logging.getLogger(__name__)
+
+
+class PerformanceManager:
+    """Runtime performance tuning and diagnostics."""
+
+    def __init__(self, config_path: str = "config/performance.yaml") -> None:
+        self.config: Dict = self._load_config(config_path)
+        perf = self.config.get("performance", {})
+        self.target_fps: int = int(perf.get("target_fps", 60))
+        self.clock = pygame.time.Clock() if pygame else None
+        self.asset_cache = AssetManager()
+        self.resource_log: List[str] = []
+        self.frame_times: List[float] = []
+        self.diagnostics_enabled: bool = bool(perf.get("diagnostics_enabled", False))
+        self.max_cache_size_mb: int = int(perf.get("asset_cache_limit_mb", 200))
+        self._profiles: Dict[str, Dict] = self.config.get("profiles", {})
+
+    # ------------------------------------------------------------------
+    # Config helpers
+    # ------------------------------------------------------------------
+    def _load_config(self, path: str) -> Dict:
+        if not yaml or not os.path.exists(path):
+            return {}
+        with open(path, "r", encoding="utf-8") as fh:
+            return yaml.safe_load(fh) or {}
+
+    # ------------------------------------------------------------------
+    # Framerate helpers
+    # ------------------------------------------------------------------
+    def set_target_fps(self, fps: int) -> None:
+        self.target_fps = int(fps)
+
+    def track_frame(self) -> None:
+        if not self.clock:
+            return
+        ms = self.clock.tick(self.target_fps)
+        self.frame_times.append(ms / 1000.0)
+        if len(self.frame_times) > 60:
+            self.frame_times.pop(0)
+
+    def enforce_frame_delay(self) -> None:
+        if self.clock:
+            self.clock.tick(self.target_fps)
+
+    # ------------------------------------------------------------------
+    # Diagnostics & cache helpers
+    # ------------------------------------------------------------------
+    def log_resource_usage(self) -> None:
+        if not self.diagnostics_enabled:
+            return
+        current = self.cache_size_mb()
+        msg = f"Cache size: {current:.2f} MB"
+        self.resource_log.append(msg)
+        logger.debug(msg)
+
+    def cache_size_mb(self) -> float:
+        size = 0
+        for coll in (self.asset_cache.image_cache, self.asset_cache.sound_cache, self.asset_cache.music_cache):
+            for obj in coll.values():
+                try:
+                    size += sys.getsizeof(obj)
+                except Exception:
+                    pass
+        return size / (1024 * 1024)
+
+    def clear_unused_assets(self) -> None:
+        self.asset_cache.clear_cache()
+
+    def trim_cache(self) -> None:
+        if self.cache_size_mb() > self.max_cache_size_mb:
+            self.clear_unused_assets()
+
+    def get_diagnostics(self) -> Dict:
+        avg_fps = 0.0
+        if self.frame_times:
+            avg_fps = 1.0 / (sum(self.frame_times) / len(self.frame_times))
+        return {
+            "average_fps": avg_fps,
+            "cache_size_mb": self.cache_size_mb(),
+            "frames_tracked": len(self.frame_times),
+        }
+
+    def flush_scene_cache(self, scene_id: str) -> None:
+        self.clear_unused_assets()
+
+    def apply_performance_profile(self, profile_name: str) -> None:
+        profile = self._profiles.get(profile_name, {})
+        if not profile:
+            return
+        if "target_fps" in profile:
+            self.target_fps = int(profile["target_fps"])
+        if "cache_limit" in profile:
+            self.max_cache_size_mb = int(profile["cache_limit"])
+        if "diagnostics" in profile:
+            self.diagnostics_enabled = bool(profile["diagnostics"])