diff --git a/source/funkin/ui/charSelect/CharSelectGF.hx b/source/funkin/ui/charSelect/CharSelectGF.hx
index 9c4bab961..c214d54de 100644
--- a/source/funkin/ui/charSelect/CharSelectGF.hx
+++ b/source/funkin/ui/charSelect/CharSelectGF.hx
@@ -16,8 +16,8 @@ class CharSelectGF extends FlxAtlasSprite implements IBPMSyncedScriptedClass
   var fadingStatus:FadeStatus = OFF;
   var fadeAnimIndex:Int = 0;
 
-  var animInInfo:FramesJSFLInfo;
-  var animOutInfo:FramesJSFLInfo;
+  var animInInfo:Null<FramesJSFLInfo>;
+  var animOutInfo:Null<FramesJSFLInfo>;
 
   var intendedYPos:Float = 0;
   var intendedAlpha:Float = 0;
@@ -113,8 +113,13 @@ class CharSelectGF extends FlxAtlasSprite implements IBPMSyncedScriptedClass
    * @param animInfo Should not be confused with animInInfo!
    *                 This is merely a local var for the function!
    */
-  function doFade(animInfo:FramesJSFLInfo):Void
+  function doFade(animInfo:Null<FramesJSFLInfo>):Void
   {
+    if (animInfo == null)
+    {
+      return;
+    }
+
     fadeTimer += FlxG.elapsed;
     if (fadeTimer >= 1 / 24)
     {
@@ -181,6 +186,9 @@ class CharSelectGF extends FlxAtlasSprite implements IBPMSyncedScriptedClass
 
       animInInfo = FramesJSFLParser.parse(animInfoPath + '/In.txt');
       animOutInfo = FramesJSFLParser.parse(animInfoPath + '/Out.txt');
+
+      if (animInInfo == null) trace("[ERROR] Failed to load data for animInInfo, is the path provided correct?");
+      if (animOutInfo == null) trace("[ERROR] Failed to load data for animOutInfo, is the path provided correct?");
     }
 
     playAnimation("idle", true, false, false);
diff --git a/source/funkin/ui/charSelect/CharSelectSubState.hx b/source/funkin/ui/charSelect/CharSelectSubState.hx
index 201fb9470..9c26a3984 100644
--- a/source/funkin/ui/charSelect/CharSelectSubState.hx
+++ b/source/funkin/ui/charSelect/CharSelectSubState.hx
@@ -92,7 +92,7 @@ class CharSelectSubState extends MusicBeatSubState
     new DropShadowFilter(5, 45, 0x000000, 1, 2, 2, 1, 1, false, false, false)
   ];
 
-  var bopInfo:FramesJSFLInfo;
+  var bopInfo:Null<FramesJSFLInfo>;
   var blackScreen:FunkinSprite;
 
   var charHitbox:FlxObject;
@@ -137,6 +137,10 @@ class CharSelectSubState extends MusicBeatSubState
     cutoutSize = FullScreenScaleMode.gameCutoutSize.x / 2;
 
     bopInfo = FramesJSFLParser.parse(Paths.file("images/charSelect/iconBopInfo/iconBopInfo.txt"));
+    if (bopInfo == null)
+    {
+      trace("[ERROR] Failed to load data for bopInfo, is the path provided correct?");
+    }
 
     var bg:FlxSprite = new FlxSprite(cutoutSize + -153, -140);
     bg.loadGraphic(Paths.image('charSelect/charSelectBG'));
@@ -1032,6 +1036,7 @@ class CharSelectSubState extends MusicBeatSubState
 
   function doBop(icon:PixelatedIcon, elapsed:Float):Void
   {
+    if (bopInfo == null) return;
     if (bopFr >= bopInfo.frames.length)
     {
       bopRefX = 0;
diff --git a/source/funkin/util/BezierUtil.hx b/source/funkin/util/BezierUtil.hx
index 37d91223b..aef443c01 100644
--- a/source/funkin/util/BezierUtil.hx
+++ b/source/funkin/util/BezierUtil.hx
@@ -5,6 +5,7 @@ import flixel.math.FlxPoint;
 /**
  * Utilities for performing math with bezier curves.
  */
+@:nullSafety
 class BezierUtil
 {
   /**
diff --git a/source/funkin/util/ClipboardUtil.hx b/source/funkin/util/ClipboardUtil.hx
index 2796bcad6..5302c2864 100644
--- a/source/funkin/util/ClipboardUtil.hx
+++ b/source/funkin/util/ClipboardUtil.hx
@@ -5,6 +5,7 @@ package funkin.util;
  * On platforms that don't support interacting with the clipboard,
  * an internal clipboard is used (neat!).
  */
+@:nullSafety
 class ClipboardUtil
 {
   /**
@@ -14,7 +15,7 @@ class ClipboardUtil
    * @param	once If true, the callback will only execute once and then be deleted.
    * @param priority Set the priority at which the callback will be executed. Higher values execute first.
    */
-  public static function addListener(callback:Void->Void, once:Bool = false, ?priority:Int = 0):Void
+  public static function addListener(callback:Void->Void, once:Bool = false, priority:Int = 0):Void
   {
     lime.system.Clipboard.onUpdate.add(callback, once, priority);
   }
diff --git a/source/funkin/util/Constants.hx b/source/funkin/util/Constants.hx
index 8de4cc983..6af1d2365 100644
--- a/source/funkin/util/Constants.hx
+++ b/source/funkin/util/Constants.hx
@@ -8,6 +8,7 @@ import lime.app.Application;
 /**
  * A store of unchanging, globally relevant values.
  */
+@:nullSafety
 class Constants
 {
   /**
diff --git a/source/funkin/util/DateUtil.hx b/source/funkin/util/DateUtil.hx
index f899ffeb2..2ae378d2e 100644
--- a/source/funkin/util/DateUtil.hx
+++ b/source/funkin/util/DateUtil.hx
@@ -3,9 +3,10 @@ package funkin.util;
 /**
  * Utilities for performing operations on dates.
  */
+@:nullSafety
 class DateUtil
 {
-  public static function generateTimestamp(?date:Date = null):String
+  public static function generateTimestamp(?date:Date):String
   {
     if (date == null) date = Date.now();
 
@@ -13,7 +14,7 @@ class DateUtil
       '${date.getFullYear()}-${Std.string(date.getMonth() + 1).lpad('0', 2)}-${Std.string(date.getDate()).lpad('0', 2)}-${Std.string(date.getHours()).lpad('0', 2)}-${Std.string(date.getMinutes()).lpad('0', 2)}-${Std.string(date.getSeconds()).lpad('0', 2)}';
   }
 
-  public static function generateCleanTimestamp(?date:Date = null):String
+  public static function generateCleanTimestamp(?date:Date):String
   {
     if (date == null) date = Date.now();
 
diff --git a/source/funkin/util/EaseUtil.hx b/source/funkin/util/EaseUtil.hx
index 200e74d07..c6f817d2c 100644
--- a/source/funkin/util/EaseUtil.hx
+++ b/source/funkin/util/EaseUtil.hx
@@ -1,5 +1,6 @@
 package funkin.util;
 
+@:nullSafety
 class EaseUtil
 {
   /**
diff --git a/source/funkin/util/FlxColorUtil.hx b/source/funkin/util/FlxColorUtil.hx
index 429d536d8..adca6df24 100644
--- a/source/funkin/util/FlxColorUtil.hx
+++ b/source/funkin/util/FlxColorUtil.hx
@@ -5,6 +5,7 @@ import flixel.util.FlxColor;
 /**
  * Non inline FlxColor functions for use in hscript files
  */
+@:nullSafety
 class FlxColorUtil
 {
   /**
diff --git a/source/funkin/util/FlxGamepadUtil.hx b/source/funkin/util/FlxGamepadUtil.hx
index 4fea7500b..738161cd0 100644
--- a/source/funkin/util/FlxGamepadUtil.hx
+++ b/source/funkin/util/FlxGamepadUtil.hx
@@ -8,6 +8,7 @@ import lime.ui.GamepadButton as LimeGamepadButton;
 /**
  * Utilities for working with Flixel gamepads.
  */
+@:nullSafety
 class FlxGamepadUtil
 {
   public static function getInputID(gamepad:FlxGamepad, button:LimeGamepadButton):FlxGamepadInputID
@@ -33,14 +34,14 @@ class FlxGamepadUtil
     #end
   }
 
-  @:privateAccess
   public static function getFlxGamepadByLimeGamepad(gamepad:LimeGamepad):FlxGamepad
   {
     // Why is this so elaborate?
     @:privateAccess
-    var gameInputDevice:openfl.ui.GameInputDevice = openfl.ui.GameInput.__getDevice(gamepad);
-    @:privateAccess
-    var gamepadIndex:Int = FlxG.gamepads.findGamepadIndex(gameInputDevice);
-    return FlxG.gamepads.getByID(gamepadIndex);
+    {
+      var gameInputDevice:openfl.ui.GameInputDevice = openfl.ui.GameInput.__getDevice(gamepad);
+      var gamepadIndex:Int = FlxG.gamepads.findGamepadIndex(gameInputDevice);
+      return FlxG.gamepads.getByID(gamepadIndex);
+    }
   }
 }
diff --git a/source/funkin/util/FlxTweenUtil.hx b/source/funkin/util/FlxTweenUtil.hx
index 4a8806bf8..d091b5754 100644
--- a/source/funkin/util/FlxTweenUtil.hx
+++ b/source/funkin/util/FlxTweenUtil.hx
@@ -2,6 +2,7 @@ package funkin.util;
 
 import flixel.tweens.FlxTween;
 
+@:nullSafety
 class FlxTweenUtil
 {
   public static function pauseTween(tween:FlxTween):Void
diff --git a/source/funkin/util/FramesJSFLParser.hx b/source/funkin/util/FramesJSFLParser.hx
index 3a9ff8d0a..ca3d349e6 100644
--- a/source/funkin/util/FramesJSFLParser.hx
+++ b/source/funkin/util/FramesJSFLParser.hx
@@ -7,13 +7,17 @@ import openfl.Assets;
  * Homemade dipshit proprietary format to get simple animation info out of flash!
  * Pure convienience!
  */
+@:nullSafety
 class FramesJSFLParser
 {
-  public static function parse(path:String):FramesJSFLInfo
+  public static function parse(path:String):Null<FramesJSFLInfo>
   {
     var text:String = Assets.getText(path);
-
-    // TODO: error handle if text is null
+    if (text == null)
+    {
+      trace('[ERROR] Could not load FramesJSFL data asset from path $path');
+      return null;
+    }
 
     var output:FramesJSFLInfo = {frames: []};
 
diff --git a/source/funkin/util/HaxeUIUtil.hx b/source/funkin/util/HaxeUIUtil.hx
index 1ffd9cd40..d063a5b19 100644
--- a/source/funkin/util/HaxeUIUtil.hx
+++ b/source/funkin/util/HaxeUIUtil.hx
@@ -2,16 +2,17 @@ package funkin.util;
 
 import haxe.ui.tooltips.ToolTipRegionOptions;
 
+@:nullSafety
 class HaxeUIUtil
 {
-  public static function buildTooltip(text:String, ?left:Float, ?top:Float, ?width:Float, ?height:Float):ToolTipRegionOptions
+  public static function buildTooltip(text:String, left:Float = 0.0, top:Float = 0.0, width:Float = 0.0, height:Float = 0.0):ToolTipRegionOptions
   {
     return {
       tipData: {text: text},
-      left: left ?? 0.0,
-      top: top ?? 0.0,
-      width: width ?? 0.0,
-      height: height ?? 0.0
+      left: left,
+      top: top,
+      width: width,
+      height: height
     }
   }
 }
diff --git a/source/funkin/util/InputUtil.hx b/source/funkin/util/InputUtil.hx
index 8f4fcc55f..17e9ececa 100644
--- a/source/funkin/util/InputUtil.hx
+++ b/source/funkin/util/InputUtil.hx
@@ -2,6 +2,7 @@ package funkin.util;
 
 import funkin.input.Controls.Device;
 import flixel.input.gamepad.FlxGamepad;
+import flixel.input.gamepad.FlxGamepadInputID;
 import flixel.input.keyboard.FlxKey;
 
 using flixel.util.FlxStringUtil;
@@ -9,6 +10,7 @@ using flixel.util.FlxStringUtil;
 /**
  * Utilities for working with inputs.
  */
+@:nullSafety
 class InputUtil
 {
   public static function format(id:Int, device:Device):String
@@ -79,7 +81,7 @@ class InputUtil
       case NUMPADPLUS: "#+";
       case NUMPADPERIOD: "#.";
       case NUMPADMULTIPLY: "#*";
-      default: titleCase(FlxKey.toStringMap[id]);
+      default: titleCase(FlxKey.toStringMap[id] ?? '?');
     }
   }
 
@@ -89,12 +91,12 @@ class InputUtil
   {
     return switch (gamepad.getInputLabel(id))
     {
-      // case null | "": shortenButtonName(FlxGamepadInputID.toStringMap[id]);
+      case null, "": shortenButtonName(FlxGamepadInputID.toStringMap[id]);
       case label: shortenButtonName(label);
     }
   }
 
-  static function shortenButtonName(name:String)
+  static function shortenButtonName(name:Null<String>)
   {
     return switch (name == null ? "" : name.toLowerCase())
     {
@@ -145,6 +147,7 @@ class InputUtil
   }
 }
 
+@:nullSafety
 @:forward
 enum abstract ControllerName(String) from String to String
 {
@@ -170,7 +173,7 @@ enum abstract ControllerName(String) from String to String
     }
   }
 
-  static public function getAsset(gamepad:FlxGamepad):String
+  static public function getAsset(gamepad:Null<FlxGamepad>):String
   {
     if (gamepad == null) return 'assets/images/ui/devices/Keys.png';
 
diff --git a/source/funkin/util/MathUtil.hx b/source/funkin/util/MathUtil.hx
index 0ba113a1e..41624fd91 100644
--- a/source/funkin/util/MathUtil.hx
+++ b/source/funkin/util/MathUtil.hx
@@ -3,6 +3,7 @@ package funkin.util;
 /**
  * Utilities for performing mathematical operations.
  */
+@:nullSafety
 class MathUtil
 {
   /**
@@ -56,7 +57,7 @@ class MathUtil
     return (result == Math.NaN) ? 1.0 : result;
   }
 
-  public static function easeInOutBack(x:Float, ?c:Float = 1.70158):Float
+  public static function easeInOutBack(x:Float, c:Float = 1.70158):Float
   {
     if (x <= 0.0) return 0.0;
     if (x >= 1.0) return 1.0;
@@ -64,14 +65,14 @@ class MathUtil
     return (result == Math.NaN) ? 1.0 : result;
   }
 
-  public static function easeInBack(x:Float, ?c:Float = 1.70158):Float
+  public static function easeInBack(x:Float, c:Float = 1.70158):Float
   {
     if (x <= 0.0) return 0.0;
     if (x >= 1.0) return 1.0;
     return (1 + c) * x * x * x - c * x * x;
   }
 
-  public static function easeOutBack(x:Float, ?c:Float = 1.70158):Float
+  public static function easeOutBack(x:Float, c:Float = 1.70158):Float
   {
     if (x <= 0.0) return 0.0;
     if (x >= 1.0) return 1.0;
diff --git a/source/funkin/util/MemoryUtil.hx b/source/funkin/util/MemoryUtil.hx
index 10b38c03a..3e9239bf9 100644
--- a/source/funkin/util/MemoryUtil.hx
+++ b/source/funkin/util/MemoryUtil.hx
@@ -11,6 +11,7 @@ package funkin.util;
  * @see https://github.com/HaxeFoundation/hxcpp/blob/master/docs/build_xml/Defines.md
  * @see cpp.vm.Gc
  */
+@:nullSafety
 class MemoryUtil
 {
   public static function buildGCInfo():String
diff --git a/source/funkin/util/MouseUtil.hx b/source/funkin/util/MouseUtil.hx
index fa498a9a5..59bb7eef2 100644
--- a/source/funkin/util/MouseUtil.hx
+++ b/source/funkin/util/MouseUtil.hx
@@ -5,6 +5,7 @@ import flixel.math.FlxPoint;
 /**
  * Utility functions related to the mouse.
  */
+@:nullSafety
 class MouseUtil
 {
   static var oldCamPos:FlxPoint = new FlxPoint();
diff --git a/source/funkin/util/PlatformUtil.hx b/source/funkin/util/PlatformUtil.hx
index ae8c1dcee..f9554406f 100644
--- a/source/funkin/util/PlatformUtil.hx
+++ b/source/funkin/util/PlatformUtil.hx
@@ -3,6 +3,7 @@ package funkin.util;
 /**
  * Utility functions related to specific platforms.
  */
+@:nullSafety
 class PlatformUtil
 {
   /**
diff --git a/source/funkin/util/SerializerUtil.hx b/source/funkin/util/SerializerUtil.hx
index b94a1066e..cc7e3b5d1 100644
--- a/source/funkin/util/SerializerUtil.hx
+++ b/source/funkin/util/SerializerUtil.hx
@@ -14,6 +14,7 @@ typedef ScoreInput =
  * Functions dedicated to serializing and deserializing data.
  * NOTE: Use `json2object` wherever possible, it's way more efficient.
  */
+@:nullSafety
 class SerializerUtil
 {
   static final INDENT_CHAR = "\t";
@@ -48,7 +49,7 @@ class SerializerUtil
   /**
    * Convert a JSON byte array to a Haxe object.
    */
-  public static function fromJSONBytes(input:Bytes):Dynamic
+  public static function fromJSONBytes(input:Bytes):Null<Dynamic>
   {
     try
     {
diff --git a/source/funkin/util/SortUtil.hx b/source/funkin/util/SortUtil.hx
index f6d3721f0..96e7a2028 100644
--- a/source/funkin/util/SortUtil.hx
+++ b/source/funkin/util/SortUtil.hx
@@ -22,6 +22,7 @@ import funkin.data.song.SongData.SongNoteData;
  *    You may consider using one of the functions in `funkin.util.tools.ArraySortTools` instead.
  * NOTE: Both sort functions modify the array in-place. You may consider using `Reflect.copy()` to make a copy of the array before sorting.
  */
+@:nullSafety
 class SortUtil
 {
   /**
@@ -97,7 +98,7 @@ class SortUtil
    * @param b The second string to compare.
    * @return 1 if `a` comes before `b`, -1 if `b` comes before `a`, 0 if they are equal
    */
-  public static function alphabetically(?a:String, ?b:String):Int
+  public static function alphabetically(a:String, b:String):Int
   {
     a = a.toUpperCase();
     b = b.toUpperCase();
diff --git a/source/funkin/util/TrackerToolButtonUtil.hx b/source/funkin/util/TrackerToolButtonUtil.hx
index 161d92650..7000a8737 100644
--- a/source/funkin/util/TrackerToolButtonUtil.hx
+++ b/source/funkin/util/TrackerToolButtonUtil.hx
@@ -9,6 +9,7 @@ import flixel.system.debug.interaction.tools.Tool;
  * FlxDebugger Interaction window, which when pressed will open a
  * tracking window corresponding to whatever currently selected objects are
  */
+@:nullSafety
 class TrackerToolButtonUtil extends Tool
 {
   override function init(brain:Interaction):Tool
diff --git a/source/funkin/util/TrackerUtil.hx b/source/funkin/util/TrackerUtil.hx
index a2552f63e..e6a1e953d 100644
--- a/source/funkin/util/TrackerUtil.hx
+++ b/source/funkin/util/TrackerUtil.hx
@@ -7,6 +7,7 @@ import flixel.FlxG;
 /**
  * Utility class that helps manage adding profiles to the flixel debugger tracker
  */
+@:nullSafety
 class TrackerUtil
 {
   /**
diff --git a/source/funkin/util/VersionUtil.hx b/source/funkin/util/VersionUtil.hx
index 475275cb3..f8ee61377 100644
--- a/source/funkin/util/VersionUtil.hx
+++ b/source/funkin/util/VersionUtil.hx
@@ -9,6 +9,7 @@ import thx.semver.Version.Identifier.StringId;
  * increment the minor version (1.x.0) if you make a new feature (but previous content is still compatible),
  * and increment the major version (x.0.0) if you make a breaking change (e.g. new API or reorganized file format).
  */
+@:nullSafety
 class VersionUtil
 {
   /**
@@ -32,6 +33,7 @@ class VersionUtil
     }
   }
 
+  @:nullSafety(Off)
   public static function repairVersion(version:thx.semver.Version):thx.semver.Version
   {
     var versionData:thx.semver.Version.SemVer = version;
@@ -109,7 +111,7 @@ class VersionUtil
    * @param input The JSON string to parse.
    * @return The semantic version, or null if it could not be parsed.
    */
-  public static function parseVersion(input:Dynamic):Null<thx.semver.Version>
+  public static function parseVersion(input:Null<Dynamic>):Null<thx.semver.Version>
   {
     if (input == null) return null;
 
diff --git a/source/funkin/util/WindowUtil.hx b/source/funkin/util/WindowUtil.hx
index 38076c5bd..85734c6fc 100644
--- a/source/funkin/util/WindowUtil.hx
+++ b/source/funkin/util/WindowUtil.hx
@@ -14,6 +14,7 @@ using StringTools;
 #include <psapi.h>
 ')
 #end
+@:nullSafety
 class WindowUtil
 {
   /**
diff --git a/source/funkin/util/assets/DataAssets.hx b/source/funkin/util/assets/DataAssets.hx
index b38c993fe..8f827ad06 100644
--- a/source/funkin/util/assets/DataAssets.hx
+++ b/source/funkin/util/assets/DataAssets.hx
@@ -1,5 +1,6 @@
 package funkin.util.assets;
 
+@:nullSafety
 class DataAssets
 {
   static function buildDataPath(path:String):String
@@ -7,7 +8,7 @@ class DataAssets
     return 'assets/data/${path}';
   }
 
-  public static function listDataFilesInPath(path:String, ?suffix:String = '.json'):Array<String>
+  public static function listDataFilesInPath(path:String, suffix:String = '.json'):Array<String>
   {
     var textAssets = openfl.utils.Assets.list(TEXT);
 
diff --git a/source/funkin/util/assets/FlxAnimationUtil.hx b/source/funkin/util/assets/FlxAnimationUtil.hx
index ee5b0edec..cf435cdff 100644
--- a/source/funkin/util/assets/FlxAnimationUtil.hx
+++ b/source/funkin/util/assets/FlxAnimationUtil.hx
@@ -4,6 +4,7 @@ import flixel.FlxSprite;
 import flixel.graphics.frames.FlxFramesCollection;
 import funkin.data.animation.AnimationData;
 
+@:nullSafety
 class FlxAnimationUtil
 {
   /**
@@ -11,6 +12,7 @@ class FlxAnimationUtil
    */
   public static function addAtlasAnimation(target:FlxSprite, anim:AnimationData):Void
   {
+    if (anim.prefix == null) return;
     var frameRate = anim.frameRate == null ? 24 : anim.frameRate;
     var looped = anim.looped == null ? false : anim.looped;
     var flipX = anim.flipX == null ? false : anim.flipX;
@@ -49,6 +51,7 @@ class FlxAnimationUtil
    */
   public static function combineFramesCollections(a:FlxFramesCollection, b:FlxFramesCollection):FlxFramesCollection
   {
+    @:nullSafety(Off)
     var result:FlxFramesCollection = new FlxFramesCollection(null, ATLAS, null);
 
     for (frame in a.frames)
diff --git a/source/funkin/util/assets/SoundUtil.hx b/source/funkin/util/assets/SoundUtil.hx
index 0b932cd0c..8af62e4d9 100644
--- a/source/funkin/util/assets/SoundUtil.hx
+++ b/source/funkin/util/assets/SoundUtil.hx
@@ -5,6 +5,7 @@ import openfl.media.Sound as OpenFLSound;
 import funkin.audio.FunkinSound;
 import lime.media.AudioBuffer;
 
+@:nullSafety
 class SoundUtil
 {
   /**
@@ -18,7 +19,7 @@ class SoundUtil
     if (input == null) return null;
 
     var openflSound:OpenFLSound = OpenFLSound.fromAudioBuffer(AudioBuffer.fromBytes(input));
-    var output:FunkinSound = FunkinSound.load(openflSound, 1.0, false);
-    return output;
+    if (openflSound == null) return null;
+    return FunkinSound.load(openflSound, 1.0, false);
   }
 }
diff --git a/source/funkin/util/logging/AnsiTrace.hx b/source/funkin/util/logging/AnsiTrace.hx
index 552489327..e59561489 100644
--- a/source/funkin/util/logging/AnsiTrace.hx
+++ b/source/funkin/util/logging/AnsiTrace.hx
@@ -1,5 +1,6 @@
 package funkin.util.logging;
 
+@:nullSafety
 class AnsiTrace
 {
   /**
@@ -41,7 +42,7 @@ class AnsiTrace
    * Format the output to use ANSI colors.
    * Edited from the standard `trace()` implementation.
    */
-  public static function formatOutput(v:Dynamic, infos:haxe.PosInfos):String
+  public static function formatOutput(v:Dynamic, ?infos:haxe.PosInfos):String
   {
     var str = Std.string(v);
     if (infos == null) return str;
diff --git a/source/funkin/util/logging/Perf.hx b/source/funkin/util/logging/Perf.hx
index 83da7a32f..2940985d4 100644
--- a/source/funkin/util/logging/Perf.hx
+++ b/source/funkin/util/logging/Perf.hx
@@ -12,6 +12,7 @@ package funkin.util.logging;
  * perf.print();
  * ```
  */
+@:nullSafety
 class Perf
 {
   final startTime:Float;
diff --git a/source/funkin/util/macro/ClassMacro.hx b/source/funkin/util/macro/ClassMacro.hx
index 0918d4085..9d15508ce 100644
--- a/source/funkin/util/macro/ClassMacro.hx
+++ b/source/funkin/util/macro/ClassMacro.hx
@@ -10,6 +10,7 @@ import haxe.macro.Type.ClassType;
  * This code is a bitch glad Jason figured it out.
  * Based on code from CompileTime: https://github.com/jasononeil/compiletime
  */
+@:nullSafety
 class ClassMacro
 {
   /**
diff --git a/source/funkin/util/macro/CompiledClassList.hx b/source/funkin/util/macro/CompiledClassList.hx
index 68415b1be..e7ad721ac 100644
--- a/source/funkin/util/macro/CompiledClassList.hx
+++ b/source/funkin/util/macro/CompiledClassList.hx
@@ -5,9 +5,11 @@ import haxe.rtti.Meta;
 /**
  * A complement to `ClassMacro`. See `ClassMacro` for more information.
  */
+@:nullSafety
 class CompiledClassList
 {
-  static var classLists:Map<String, List<Class<Dynamic>>>;
+  static var classLists:Map<String, List<Class<Dynamic>>> = [];
+  static var initialized:Bool = false;
 
   /**
    * Class lists are injected into this class's metadata during the typing phase.
@@ -15,7 +17,7 @@ class CompiledClassList
    */
   static function init():Void
   {
-    classLists = [];
+    initialized = true;
 
     // Meta.getType returns Dynamic<Array<Dynamic>>.
     var metaData = Meta.getType(CompiledClassList);
@@ -48,9 +50,9 @@ class CompiledClassList
     }
   }
 
-  public static function get(request:String):List<Class<Dynamic>>
+  public static function get(request:String):Null<List<Class<Dynamic>>>
   {
-    if (classLists == null) init();
+    if (!initialized) init();
 
     if (!classLists.exists(request))
     {
diff --git a/source/funkin/util/macro/FlxMacro.hx b/source/funkin/util/macro/FlxMacro.hx
index cec6b72ec..b31a0a03a 100644
--- a/source/funkin/util/macro/FlxMacro.hx
+++ b/source/funkin/util/macro/FlxMacro.hx
@@ -2,6 +2,7 @@ package funkin.util.macro;
 
 #if !display
 #if macro
+@:nullSafety
 class FlxMacro
 {
   /**
diff --git a/source/funkin/util/macro/GitCommit.hx b/source/funkin/util/macro/GitCommit.hx
index 9e3305c41..04f173c56 100644
--- a/source/funkin/util/macro/GitCommit.hx
+++ b/source/funkin/util/macro/GitCommit.hx
@@ -1,6 +1,7 @@
 package funkin.util.macro;
 
 #if !display
+@:nullSafety
 class GitCommit
 {
   /**
diff --git a/source/funkin/util/macro/HaxelibVersions.hx b/source/funkin/util/macro/HaxelibVersions.hx
index 63cfb2bc7..76f987bfa 100644
--- a/source/funkin/util/macro/HaxelibVersions.hx
+++ b/source/funkin/util/macro/HaxelibVersions.hx
@@ -2,6 +2,7 @@ package funkin.util.macro;
 
 import haxe.io.Path;
 
+@:nullSafety
 class HaxelibVersions
 {
   public static macro function getLibraryVersions():haxe.macro.Expr.ExprOf<Array<String>>
diff --git a/source/funkin/util/macro/InlineMacro.hx b/source/funkin/util/macro/InlineMacro.hx
index c40257409..0ec6d572a 100644
--- a/source/funkin/util/macro/InlineMacro.hx
+++ b/source/funkin/util/macro/InlineMacro.hx
@@ -7,6 +7,7 @@ using funkin.util.tools.ArrayTools;
 /**
  * A macro to make fields inline.
  */
+@:nullSafety
 class InlineMacro
 {
   /**
diff --git a/source/funkin/util/macro/MacroUtil.hx b/source/funkin/util/macro/MacroUtil.hx
index bbe6e71af..d9e644194 100644
--- a/source/funkin/util/macro/MacroUtil.hx
+++ b/source/funkin/util/macro/MacroUtil.hx
@@ -7,6 +7,7 @@ import haxe.macro.Type;
 /**
  * A collection of utility functions for Haxe macros.
  */
+@:nullSafety
 class MacroUtil
 {
   /**
diff --git a/source/funkin/util/plugins/EvacuateDebugPlugin.hx b/source/funkin/util/plugins/EvacuateDebugPlugin.hx
index eb292b852..54e12300e 100644
--- a/source/funkin/util/plugins/EvacuateDebugPlugin.hx
+++ b/source/funkin/util/plugins/EvacuateDebugPlugin.hx
@@ -6,6 +6,7 @@ import flixel.FlxBasic;
  * A plugin which adds functionality to press `F4` to immediately transition to the main menu.
  * This is useful for debugging or if you get softlocked or something.
  */
+@:nullSafety
 class EvacuateDebugPlugin extends FlxBasic
 {
   public function new()
diff --git a/source/funkin/util/plugins/ForceCrashPlugin.hx b/source/funkin/util/plugins/ForceCrashPlugin.hx
index 6f402c4e0..faa2cb2e9 100644
--- a/source/funkin/util/plugins/ForceCrashPlugin.hx
+++ b/source/funkin/util/plugins/ForceCrashPlugin.hx
@@ -6,6 +6,7 @@ import flixel.FlxBasic;
  * A plugin which forcibly crashes the application.
  * TODO: Should we disable this in release builds?
  */
+@:nullSafety
 class ForceCrashPlugin extends FlxBasic
 {
   public function new()
diff --git a/source/funkin/util/plugins/MemoryGCPlugin.hx b/source/funkin/util/plugins/MemoryGCPlugin.hx
index d6fb632da..44dc486d1 100644
--- a/source/funkin/util/plugins/MemoryGCPlugin.hx
+++ b/source/funkin/util/plugins/MemoryGCPlugin.hx
@@ -5,6 +5,7 @@ import flixel.FlxBasic;
 /**
  * A plugin which adds functionality to press `Ins` to immediately perform memory garbage collection.
  */
+@:nullSafety
 class MemoryGCPlugin extends FlxBasic
 {
   public function new()
diff --git a/source/funkin/util/plugins/NewgroundsMedalPlugin.hx b/source/funkin/util/plugins/NewgroundsMedalPlugin.hx
index eb34a4940..4aa21980b 100644
--- a/source/funkin/util/plugins/NewgroundsMedalPlugin.hx
+++ b/source/funkin/util/plugins/NewgroundsMedalPlugin.hx
@@ -10,13 +10,14 @@ import funkin.graphics.adobeanimate.FlxAtlasSprite;
 import flixel.math.FlxRect;
 import funkin.api.newgrounds.Medals;
 
+@:nullSafety
 class NewgroundsMedalPlugin extends FlxTypedContainer<FlxBasic>
 {
-  var medal:FlxAtlasSprite = null;
-  var points:FlxText = null;
-  var name:FlxText = null;
+  var medal:FlxAtlasSprite;
+  var points:FlxText;
+  var name:FlxText;
 
-  public static var instance:NewgroundsMedalPlugin = null;
+  public static var instance:Null<NewgroundsMedalPlugin> = null;
 
   var tween:Bool = false;
 
@@ -65,7 +66,7 @@ class NewgroundsMedalPlugin extends FlxTypedContainer<FlxBasic>
     medal.visible = false;
 
     var fr = medal.anim.curSymbol.timeline.get(0).get(0);
-    fr.name = "START"; // woerkaround
+    if (fr != null) fr.name = "START"; // woerkaround
     // fr.add(() -> FunkinSound.playOnce(Paths.sound('NGFadeIn'), 1.));
 
     medal.anim.getFrameLabel("show").add(function() {
@@ -73,6 +74,8 @@ class NewgroundsMedalPlugin extends FlxTypedContainer<FlxBasic>
       name.visible = true;
       if (name.width > name.clipRect.width)
       {
+        // TODO: Remove this once FlxText.get_size deals with TextFormat's nullable size properly
+        @:nullSafety(Off)
         am = (name.text.length * (name.size + 2) * 1.25) / name.clipRect.width * 10;
         tween = true;
         // FlxTimer.wait(0.3, () -> tween = true);
@@ -115,7 +118,9 @@ class NewgroundsMedalPlugin extends FlxTypedContainer<FlxBasic>
     instance = new NewgroundsMedalPlugin();
     FlxG.plugins.addPlugin(instance);
 
-    instance.medal.anim.onComplete.add(function() {
+    // instance is defined above so there's no need to worry about null safety here
+    @:nullSafety(Off)
+    instance.medal.anim?.onComplete.add(function() {
       if (instance.funcs.length > 0)
       {
         instance.funcs.shift()();
@@ -123,8 +128,9 @@ class NewgroundsMedalPlugin extends FlxTypedContainer<FlxBasic>
     });
   }
 
-  public static function play(points:Int = 100, name:String = "I LOVE CUM I LOVE CUM I LOVE CUM I LOVE CUM", graphic:FlxGraphic = null)
+  public static function play(points:Int = 100, name:String = "I LOVE CUM I LOVE CUM I LOVE CUM I LOVE CUM", ?graphic:FlxGraphic)
   {
+    if (instance == null) return;
     var func = function() {
       instance.points.visible = false;
       instance.name.visible = false;
diff --git a/source/funkin/util/plugins/ReloadAssetsDebugPlugin.hx b/source/funkin/util/plugins/ReloadAssetsDebugPlugin.hx
index 0e1e238ac..b4a3d8a90 100644
--- a/source/funkin/util/plugins/ReloadAssetsDebugPlugin.hx
+++ b/source/funkin/util/plugins/ReloadAssetsDebugPlugin.hx
@@ -9,6 +9,7 @@ import funkin.ui.MusicBeatSubState;
  * A plugin which adds functionality to press `F5` to reload all game assets, then reload the current state.
  * This is useful for hot reloading assets during development.
  */
+@:nullSafety
 class ReloadAssetsDebugPlugin extends FlxBasic
 {
   public function new()
diff --git a/source/funkin/util/plugins/VolumePlugin.hx b/source/funkin/util/plugins/VolumePlugin.hx
index 9fdb65558..83ad9ae3e 100644
--- a/source/funkin/util/plugins/VolumePlugin.hx
+++ b/source/funkin/util/plugins/VolumePlugin.hx
@@ -5,6 +5,7 @@ import flixel.FlxBasic;
 /**
  * Handles volume control in a way that is compatible with alternate control schemes.
  */
+@:nullSafety
 class VolumePlugin extends FlxBasic
 {
   public function new()
diff --git a/source/funkin/util/tools/ArraySortTools.hx b/source/funkin/util/tools/ArraySortTools.hx
index 9a3f8b349..37800136a 100644
--- a/source/funkin/util/tools/ArraySortTools.hx
+++ b/source/funkin/util/tools/ArraySortTools.hx
@@ -4,6 +4,7 @@ package funkin.util.tools;
  * Contains code for sorting arrays using various algorithms.
  * @see https://algs4.cs.princeton.edu/20sorting/
  */
+@:nullSafety
 class ArraySortTools
 {
   /**
diff --git a/source/funkin/util/tools/ArrayTools.hx b/source/funkin/util/tools/ArrayTools.hx
index ffad260a5..92ba82e7e 100644
--- a/source/funkin/util/tools/ArrayTools.hx
+++ b/source/funkin/util/tools/ArrayTools.hx
@@ -3,6 +3,7 @@ package funkin.util.tools;
 /**
  * A static extension which provides utility functions for Arrays.
  */
+@:nullSafety
 class ArrayTools
 {
   /*
diff --git a/source/funkin/util/tools/FloatTools.hx b/source/funkin/util/tools/FloatTools.hx
index e34110490..168b2605b 100644
--- a/source/funkin/util/tools/FloatTools.hx
+++ b/source/funkin/util/tools/FloatTools.hx
@@ -3,6 +3,7 @@ package funkin.util.tools;
 /**
  * Utilities for performing common math operations.
  */
+@:nullSafety
 class FloatTools
 {
   /**
@@ -16,7 +17,7 @@ class FloatTools
   /**
     Round a float to a certain number of decimal places.
   **/
-  public static function round(number:Float, ?precision = 2):Float
+  public static function round(number:Float, precision:Int = 2):Float
   {
     number *= Math.pow(10, precision);
     return Math.round(number) / Math.pow(10, precision);
diff --git a/source/funkin/util/tools/ICloneable.hx b/source/funkin/util/tools/ICloneable.hx
index 33f19f167..49679fd0b 100644
--- a/source/funkin/util/tools/ICloneable.hx
+++ b/source/funkin/util/tools/ICloneable.hx
@@ -4,6 +4,7 @@ package funkin.util.tools;
  * Implement this on a class to enable `Array<T>.deepClone()` to work on it.
  * NOTE: T should be the type of the class that implements this interface.
  */
+@:nullSafety
 interface ICloneable<T>
 {
   public function clone():T;
diff --git a/source/funkin/util/tools/Int64Tools.hx b/source/funkin/util/tools/Int64Tools.hx
index b6ac84ade..a63f708e0 100644
--- a/source/funkin/util/tools/Int64Tools.hx
+++ b/source/funkin/util/tools/Int64Tools.hx
@@ -5,6 +5,7 @@ import haxe.Int64;
 /**
  * Why `haxe.Int64` doesn't have a built-in `toFloat` function is beyond me.
  */
+@:nullSafety
 class Int64Tools
 {
   private inline static var MAX_32_PRECISION:Float = 4294967296.0;
diff --git a/source/funkin/util/tools/IntTools.hx b/source/funkin/util/tools/IntTools.hx
index 1d660ad1b..5e61aac69 100644
--- a/source/funkin/util/tools/IntTools.hx
+++ b/source/funkin/util/tools/IntTools.hx
@@ -3,6 +3,7 @@ package funkin.util.tools;
 /**
  * Utilities for performing common math operations.
  */
+@:nullSafety
 class IntTools
 {
   /**
diff --git a/source/funkin/util/tools/IteratorTools.hx b/source/funkin/util/tools/IteratorTools.hx
index 49d9477f6..2297eedf7 100644
--- a/source/funkin/util/tools/IteratorTools.hx
+++ b/source/funkin/util/tools/IteratorTools.hx
@@ -7,6 +7,7 @@ package funkin.util.tools;
  *
  * @see https://haxe.org/manual/lf-static-extension.html
  */
+@:nullSafety
 class IteratorTools
 {
   public static function array<T>(iterator:Iterator<T>):Array<T>
diff --git a/source/funkin/util/tools/MapTools.hx b/source/funkin/util/tools/MapTools.hx
index 807f0aebd..65ae23b67 100644
--- a/source/funkin/util/tools/MapTools.hx
+++ b/source/funkin/util/tools/MapTools.hx
@@ -7,12 +7,13 @@ package funkin.util.tools;
  *
  * @see https://haxe.org/manual/lf-static-extension.html
  */
+@:nullSafety
 class MapTools
 {
   /**
    * Return the quantity of keys in the map.
    */
-  public static function size<K, T>(map:Map<K, T>):Int
+  public static function size<K, T>(map:Null<Map<K, T>>):Int
   {
     if (map == null) return 0;
     return map.keys().array().length;
@@ -21,7 +22,7 @@ class MapTools
   /**
    * Return a list of values from the map, as an array.
    */
-  public static function values<K, T>(map:Map<K, T>):Array<T>
+  public static function values<K, T>(map:Null<Map<K, T>>):Array<T>
   {
     if (map == null) return [];
     return [for (i in map.iterator()) i];
@@ -30,7 +31,7 @@ class MapTools
   /**
    * Create a new array with all elements of the given array, to prevent modifying the original.
    */
-  public static function clone<K, T>(map:Map<K, T>):Map<K, T>
+  public static function clone<K, T>(map:Null<Map<K, T>>):Null<Map<K, T>>
   {
     if (map == null) return null;
     return map.copy();
@@ -77,7 +78,7 @@ class MapTools
    * Return a list of keys from the map (as an array, rather than an iterator).
    * TODO: Rename this?
    */
-  public static function keyValues<K, T>(map:Map<K, T>):Array<K>
+  public static function keyValues<K, T>(map:Null<Map<K, T>>):Array<K>
   {
     if (map == null) return [];
     return map.keys().array();
diff --git a/source/funkin/util/tools/SongEventDataArrayTools.hx b/source/funkin/util/tools/SongEventDataArrayTools.hx
index 38e298dde..5ecb151a6 100644
--- a/source/funkin/util/tools/SongEventDataArrayTools.hx
+++ b/source/funkin/util/tools/SongEventDataArrayTools.hx
@@ -5,6 +5,7 @@ import funkin.data.song.SongData.SongEventData;
 /**
  * A static extension which provides utility functions for `Array<SongEventData>`s.
  */
+@:nullSafety
 class SongEventDataArrayTools
 {
   /**
diff --git a/source/funkin/util/tools/SongNoteDataArrayTools.hx b/source/funkin/util/tools/SongNoteDataArrayTools.hx
index b93303b81..28e1e90e9 100644
--- a/source/funkin/util/tools/SongNoteDataArrayTools.hx
+++ b/source/funkin/util/tools/SongNoteDataArrayTools.hx
@@ -5,6 +5,7 @@ import funkin.data.song.SongData.SongNoteData;
 /**
  * A static extension which provides utility functions for `Array<SongNoteData>`s.
  */
+@:nullSafety
 class SongNoteDataArrayTools
 {
   /**
diff --git a/source/funkin/util/tools/StringTools.hx b/source/funkin/util/tools/StringTools.hx
index cb660db05..92fa10d56 100644
--- a/source/funkin/util/tools/StringTools.hx
+++ b/source/funkin/util/tools/StringTools.hx
@@ -3,6 +3,7 @@ package funkin.util.tools;
 /**
  * A static extension which provides utility functions for Strings.
  */
+@:nullSafety
 class StringTools
 {
   /**