diff --git a/BeefLibs/Beefy2D/src/Utils.bf b/BeefLibs/Beefy2D/src/Utils.bf
index 4be4bd5d..6319db24 100644
--- a/BeefLibs/Beefy2D/src/Utils.bf
+++ b/BeefLibs/Beefy2D/src/Utils.bf
@@ -165,7 +165,7 @@ namespace Beefy
 			// Retry for a while if the other side is still writing out the file
 			for (int i = 0; i < 100; i++)
 			{
-				if (sr.Open(fileName) case .Err(let fileOpenErr))
+				if (sr.Open(fileName, .Read, .Read) case .Err(let fileOpenErr))
 				{
 					bool retry = false;
 					if (autoRetry)
diff --git a/BeefLibs/corlib/src/Span.bf b/BeefLibs/corlib/src/Span.bf
index 540e388b..091c0bae 100644
--- a/BeefLibs/corlib/src/Span.bf
+++ b/BeefLibs/corlib/src/Span.bf
@@ -272,5 +272,124 @@ namespace System
 		}
 	}
 
+#if BF_RUNTIME_CHECKS
+#define BF_OPTSPAN_LENGTH
+#endif
+
+	struct OptSpan<T>
+	{
+		protected T* mPtr;
+#if BF_OPTSPAN_LENGTH
+		protected int mLength;
+#endif
+
+		public this()
+		{
+			mPtr = null;
+#if BF_OPTSPAN_LENGTH
+			mLength = 0;
+#endif
+		}
+
+		public this(T[] array)
+		{
+			mPtr = &array.getRef(0);
+#if BF_OPTSPAN_LENGTH
+			mLength = array.[Friend]mLength;
+#endif
+		}
+
+		public this(T[] array, int index)
+		{
+			mPtr = &array[index];
+#if BF_OPTSPAN_LENGTH
+			mLength = array.[Friend]mLength - index;
+#endif
+		}
+
+		public this(T[] array, int index, int length)
+		{
+			if (length == 0)
+				mPtr = null;
+			else
+				mPtr = &array[index];
+#if BF_OPTSPAN_LENGTH
+			mLength = length;
+#endif
+		}
+
+		public this(T* memory, int length)
+		{
+			mPtr = memory;
+#if BF_OPTSPAN_LENGTH
+			mLength = length;
+#endif
+		}
+
+		public static implicit operator OptSpan<T> (T[] array)
+		{
+			return OptSpan<T>(array);
+		}
+
+
+		[Inline]
+		public T* Ptr
+		{
+			get
+			{
+				return mPtr;
+			}
+		}
+
+		public ref T this[int index]
+	    {
+			[Inline, Checked]
+	        get
+			{
+#if BF_OPTSPAN_LENGTH
+				Debug.Assert((uint)index < (uint)mLength);
+#endif
+				return ref mPtr[index];
+			}
+
+			[Inline, Unchecked]
+			get
+			{
+				return ref mPtr[index];
+			}
+	    }
+
+		public OptSpan<T> Slice(int index, int length)
+		{
+			OptSpan<T> span;
+			span.mPtr = mPtr + index;
+#if BF_OPTSPAN_LENGTH
+			Debug.Assert((uint)index + (uint)length <= (uint)mLength);
+			span.mLength = length;
+#else
+			Debug.Assert(index >= 0);
+#endif
+			return span;
+		}
+
+		public void Adjust(int ofs) mut
+		{
+			mPtr += ofs;
+#if BF_OPTSPAN_LENGTH
+			Debug.Assert((uint)ofs <= (uint)mLength);
+			mLength -= ofs;
+#endif
+		}
+
+		public OptSpan<uint8> ToRawData()
+		{
+#if BF_OPTSPAN_LENGTH
+			return OptSpan<uint8>((uint8*)mPtr, mLength * alignof(T));
+#else
+			return OptSpan<uint8>((uint8*)mPtr, 0);
+#endif			
+		}
+	}
+
 	//TODO: Make a ReadOnlySpan
 }
diff --git a/IDE/BeefProj.toml b/IDE/BeefProj.toml
index 73ad54d9..9f62fbd9 100644
--- a/IDE/BeefProj.toml
+++ b/IDE/BeefProj.toml
@@ -20,20 +20,18 @@ ProductVersion = "0000000000000000"
 [Configs.Debug.Win32]
 TargetName = ""
 OtherLinkFlags = ""
-OptimizationLevel = "O0"
 
 [Configs.Debug.Win64]
 TargetDirectory = "$(WorkspaceDir)/dist"
 TargetName = "BeefIDE_d"
 OtherLinkFlags = "$(LinkFlags) Comdlg32.lib kernel32.lib user32.lib advapi32.lib shell32.lib IDEHelper64_d.lib"
-DebugCommandArguments = "-workspace=c:\\Beef\\IDE"
+DebugCommandArguments = "-proddir=C:\\Beef\\IDE"
 DebugWorkingDirectory = "c:\\Beef\\IDE\\Tests\\EmptyTest"
 EnvironmentVars = ["_NO_DEBUG_HEAP=1"]
 
 [Configs.Release.Win32]
 TargetName = ""
 OtherLinkFlags = ""
-OptimizationLevel = "O0"
 
 [Configs.Release.Win64]
 TargetDirectory = "$(WorkspaceDir)/dist"
@@ -46,7 +44,6 @@ EnvironmentVars = ["_NO_DEBUG_HEAP=1"]
 [Configs.Debug2.Win32]
 TargetName = ""
 OtherLinkFlags = ""
-OptimizationLevel = "O0"
 
 [Configs.Debug2.Win64]
 TargetDirectory = "$(WorkspaceDir)/dist"
diff --git a/IDE/mintest/minlib/src/System/Span.bf b/IDE/mintest/minlib/src/System/Span.bf
index 478ea661..5494810b 100644
--- a/IDE/mintest/minlib/src/System/Span.bf
+++ b/IDE/mintest/minlib/src/System/Span.bf
@@ -78,14 +78,21 @@ namespace System
 			}
 		}
 
-		[Inline]
 		public ref T this[int index]
-	    {
-	        get
+		{
+			[Inline, Checked]
+		    get
+			{
+				Debug.Assert((uint)index < (uint)mLength);
+				return ref mPtr[index];
+			}
+
+			[Inline, Unchecked]
+			get
 			{
 				return ref mPtr[index];
 			}
-	    }
+		}
 
 		public Span<T> Slice(int index)
 		{
@@ -214,5 +221,124 @@ namespace System
 		}
 	}
 
+#if BF_RUNTIME_CHECKS
+#define BF_OPTSPAN_LENGTH
+#endif
+
+	struct OptSpan<T>
+	{
+		protected T* mPtr;
+#if BF_OPTSPAN_LENGTH
+		protected int mLength;
+#endif
+
+		public this()
+		{
+			mPtr = null;
+#if BF_OPTSPAN_LENGTH
+			mLength = 0;
+#endif
+		}
+
+		public this(T[] array)
+		{
+			mPtr = &array.getRef(0);
+#if BF_OPTSPAN_LENGTH
+			mLength = array.[Friend]mLength;
+#endif
+		}
+
+		public this(T[] array, int index)
+		{
+			mPtr = &array[index];
+#if BF_OPTSPAN_LENGTH
+			mLength = array.[Friend]mLength - index;
+#endif
+		}
+
+		public this(T[] array, int index, int length)
+		{
+			if (length == 0)
+				mPtr = null;
+			else
+				mPtr = &array[index];
+#if BF_OPTSPAN_LENGTH
+			mLength = length;
+#endif
+		}
+
+		public this(T* memory, int length)
+		{
+			mPtr = memory;
+#if BF_OPTSPAN_LENGTH
+			mLength = length;
+#endif
+		}
+
+		public static implicit operator OptSpan<T> (T[] array)
+		{
+			return OptSpan<T>(array);
+		}
+
+
+		[Inline]
+		public T* Ptr
+		{
+			get
+			{
+				return mPtr;
+			}
+		}
+
+		public ref T this[int index]
+	    {
+			[Inline, Checked]
+	        get
+			{
+#if BF_OPTSPAN_LENGTH
+				Debug.Assert((uint)index < (uint)mLength);
+#endif
+				return ref mPtr[index];
+			}
+
+			[Inline, Unchecked]
+			get
+			{
+				return ref mPtr[index];
+			}
+	    }
+
+		public OptSpan<T> Slice(int index, int length)
+		{
+			OptSpan<T> span;
+			span.mPtr = mPtr + index;
+#if BF_OPTSPAN_LENGTH
+			Debug.Assert((uint)index + (uint)length <= (uint)mLength);
+			span.mLength = length;
+#else
+			Debug.Assert(index >= 0);
+#endif
+			return span;
+		}
+
+		public void Adjust(int ofs) mut
+		{
+			mPtr += ofs;
+#if BF_OPTSPAN_LENGTH
+			Debug.Assert((uint)ofs <= (uint)mLength);
+			mLength -= ofs;
+#endif
+		}
+
+		public OptSpan<uint8> ToRawData()
+		{
+#if BF_OPTSPAN_LENGTH
+			return OptSpan<uint8>((uint8*)mPtr, mLength * alignof(T));
+#else
+			return OptSpan<uint8>((uint8*)mPtr, 0);
+#endif			
+		}
+	}
+
 	//TODO: Make a ReadOnlySpan
 }