diff --git a/Core/Objects/Vehicle/VehicleObject.cs b/Core/Objects/Vehicle/VehicleObject.cs
index 3a9e1cb7..61acacd9 100644
--- a/Core/Objects/Vehicle/VehicleObject.cs
+++ b/Core/Objects/Vehicle/VehicleObject.cs
@@ -256,7 +256,7 @@ public ReadOnlySpan<byte> Load(ReadOnlySpan<byte> remainingData)
 
 			// driving/start sounds
 			StartSounds.Clear();
-			var mask = 127;
+			const int mask = 127;
 			var count = NumStartSounds & mask;
 			for (var i = 0; i < count; ++i)
 			{
diff --git a/Core/Types/G1Dat.cs b/Core/Types/G1Dat.cs
index 826083a7..44c1a0e0 100644
--- a/Core/Types/G1Dat.cs
+++ b/Core/Types/G1Dat.cs
@@ -17,7 +17,7 @@ public bool TryGetImageName(int id, out string? value)
 				? BaseImageIdNameMap.TryGetValue(id, out value)
 				: (IsSteamG1 ? SteamImageIdNameMap : OtherImageIdNameMap).TryGetValue(id, out value);
 
-		public static Dictionary<int, string> BaseImageIdNameMap = new()
+		static readonly Dictionary<int, string> BaseImageIdNameMap = new()
 		{
 			{ 304, "default_palette" },
 
@@ -2147,7 +2147,7 @@ public bool TryGetImageName(int id, out string? value)
 			{ 3549, "title_menu_lesson_l" },
 		};
 
-		public static Dictionary<int, string> SteamImageIdNameMap = new()
+		static readonly Dictionary<int, string> SteamImageIdNameMap = new()
 		{
 			{ 3550, "title_menu_globe_spin_0" },
 			{ 3551, "title_menu_globe_spin_1" },
@@ -2228,7 +2228,7 @@ public bool TryGetImageName(int id, out string? value)
 			{ 3628, "owner_jailed" },
 		};
 
-		public static Dictionary<int, string> OtherImageIdNameMap = new()
+		static readonly Dictionary<int, string> OtherImageIdNameMap = new()
 		{
 			// steam G1.dat doesn't have these 2
 			{ 3550, "title_menu_lesson_a" },
diff --git a/Gui/MainForm.cs b/Gui/MainForm.cs
index d7557c3f..a099a4f8 100644
--- a/Gui/MainForm.cs
+++ b/Gui/MainForm.cs
@@ -21,7 +21,9 @@ namespace OpenLoco.ObjectEditor.Gui
 	public partial class MainForm : Form
 	{
 		readonly MainFormModel model;
+#pragma warning disable CA1859 // Use concrete types when possible for improved performance
 		readonly ILogger logger;
+#pragma warning restore CA1859 // Use concrete types when possible for improved performance
 
 		public IUiObject? CurrentUIObject
 		{
@@ -85,10 +87,10 @@ int CurrentUIImagePageNumber
 		const string GithubLatestReleaseDownloadPage = "https://github.com/OpenLoco/ObjectEditor/releases";
 		const string GithubLatestReleaseAPI = "https://api.github.com/repos/OpenLoco/ObjectEditor/releases/latest";
 
-		string SettingsPath => Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), ApplicationName);
-		string SettingsFile => Path.Combine(SettingsPath, "settings.json");
+		static string SettingsPath => Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), ApplicationName);
+		static string SettingsFile => Path.Combine(SettingsPath, "settings.json");
 
-		Version ApplicationVersion;
+		readonly Version ApplicationVersion;
 
 		public MainForm()
 		{
@@ -100,7 +102,7 @@ public MainForm()
 			};
 
 			var assembly = Assembly.GetExecutingAssembly();
-			var paletteFilename = "Gui.palette.png";
+			const string paletteFilename = "Gui.palette.png";
 			using (var stream = assembly.GetManifestResourceStream(paletteFilename))
 			{
 				//var paletteBitmap = (Bitmap)Image.FromStream(stream!);
@@ -113,7 +115,7 @@ public MainForm()
 			}
 
 			// grab current appl version from assembly
-			var versionFilename = "Gui.version.txt";
+			const string versionFilename = "Gui.version.txt";
 			using (var stream = assembly.GetManifestResourceStream(versionFilename))
 			{
 				var buf = new byte[5];
@@ -145,27 +147,17 @@ Version GetLatestVersion()
 			{
 				var jsonResponse = response.Content.ReadAsStringAsync().Result;
 				var body = JsonSerializer.Deserialize<VersionCheckBody>(jsonResponse);
-				var tagName = body?.tag_name;
-				var version = Version.Parse(tagName);
-				return version;
+				var tagName = body?.TagName;
+				if (tagName != null)
+				{
+					return Version.Parse(tagName);
+				}
 			}
+
+#pragma warning disable CA2201 // Do not raise reserved exception types
 			throw new Exception("Unable to get latest version");
+#pragma warning restore CA2201 // Do not raise reserved exception types
 		}
-		//async Task<Version> GetLatestVersionAsync()
-		//{
-		//	var client = new HttpClient();
-		//	client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("ObjectEditor", ApplicationVersion.ToString()));
-		//	var response = await client.GetAsync("https://api.github.com/repos/OpenLoco/ObjectEditor/releases/latest");
-		//	if (response.IsSuccessStatusCode)
-		//	{
-		//		var jsonResponse = await response.Content.ReadAsStringAsync();
-		//		var body = JsonSerializer.Deserialize<VersionCheckBody>(jsonResponse);
-		//		var tagName = body?.tag_name;
-		//		var version = Version.Parse(tagName);
-		//		return version;
-		//	}
-		//	throw new Exception("Unable to get latest version");
-		//}
 
 		void MainForm_Load(object sender, EventArgs e)
 		{
@@ -352,7 +344,7 @@ void InitDataCategoryTree()
 			// sound effects
 			//foreach (var sfx in model.SoundEffects)
 			{
-				var displayName = OriginalDataFiles.SoundEffect;
+				const string displayName = OriginalDataFiles.SoundEffect;
 				_ = sfxNode.Nodes.Add(displayName, displayName, 1, 1);
 			}
 
@@ -1498,9 +1490,4 @@ void tstbImageScaling_TextChanged(object sender, EventArgs e)
 			}
 		}
 	}
-
-	public class VersionCheckBody
-	{
-		public string tag_name { get; set; }
-	}
 }
diff --git a/Gui/VersionCheckBody.cs b/Gui/VersionCheckBody.cs
new file mode 100644
index 00000000..14d1ea74
--- /dev/null
+++ b/Gui/VersionCheckBody.cs
@@ -0,0 +1,4 @@
+namespace OpenLoco.ObjectEditor.Gui
+{
+	public record VersionCheckBody(string TagName);
+}