Fixed FPS issue.

FreedomFighter/Game1.cs

@@ -32,6 +32,11 @@ public class Game1 : Game
     int _fps, _fpsFrames;
     double _fpsTimer;
 
+    // precise 120Hz pacing (MonoGame's fixed-timestep Sleep overshoots and drops ticks)
+    const double TickSeconds = 1 / 120.0;
+    readonly System.Diagnostics.Stopwatch _frameClock = System.Diagnostics.Stopwatch.StartNew();
+    double _nextFrameTime;
+
     public Game1()
     {
         _graphics = new GraphicsDeviceManager(this)
@@ -42,8 +47,7 @@ public class Game1 : Game
         };
         Content.RootDirectory = "Content";
         IsMouseVisible = true;
-        IsFixedTimeStep = true;
+        IsFixedTimeStep = false;   // paced manually in EndDraw for an accurate 120Hz
-        TargetElapsedTime = TimeSpan.FromSeconds(1 / 120.0);
         Window.Title = "Freedom Fighter";
         Window.AllowUserResizing = true;
         Window.ClientSizeChanged += (_, _) =>
@@ -113,6 +117,21 @@ public class Game1 : Game
         }
     }
 
+    protected override void EndDraw()
+    {
+        base.EndDraw();
+
+        // hybrid sleep/spin wait until the next 1/120s boundary
+        _nextFrameTime += TickSeconds;
+        double now = _frameClock.Elapsed.TotalSeconds;
+        if (now > _nextFrameTime + 0.25)
+            _nextFrameTime = now;   // resync after a stall (window drag, load, etc.)
+        while (_nextFrameTime - _frameClock.Elapsed.TotalSeconds > 0.002)
+            System.Threading.Thread.Sleep(1);
+        while (_frameClock.Elapsed.TotalSeconds < _nextFrameTime)
+            System.Threading.Thread.SpinWait(50);
+    }
+
     protected override void Update(GameTime gameTime)
     {
         // all logic runs in Draw, matching the original's timer callback

FreedomFighter/Program.cs

@@ -1,5 +1,14 @@
 using System;
+using System.Runtime.InteropServices;
 
+// 1ms timer resolution so the 120Hz fixed timestep's Thread.Sleep doesn't overshoot
+// (default ~15.6ms granularity caps the loop at 80-90 FPS; OmegaTimer did the same)
+[DllImport("winmm.dll")] static extern uint timeBeginPeriod(uint ms);
+[DllImport("winmm.dll")] static extern uint timeEndPeriod(uint ms);
+timeBeginPeriod(1);
+
+try
+{
     using var game = new FreedomFighter.Game1();
     // debug aid: --shot <file> [frames] renders, saves the backbuffer to a PNG, and exits
     var cmdArgs = Environment.GetCommandLineArgs();
@@ -15,3 +24,8 @@ for (int i = 1; i < cmdArgs.Length - 1; i++)
             game.StartLevel = level;
     }
     game.Run();
+}
+finally
+{
+    timeEndPeriod(1);
+}