added some comments and polished up the code a bit

src/settings.rs

@@ -7,12 +7,14 @@ use crate::ui::UiSettings;
 const APP_DIR_NAME: &str = "desktop_dungeon_generator";
 const SETTINGS_FILE_NAME: &str = "settings.json";
 
+// Load settings JSON from the user data directory.
 pub fn load_settings() -> Option<UiSettings> {
     let path = settings_path()?;
     let content = fs::read_to_string(path).ok()?;
     serde_json::from_str::<UiSettings>(&content).ok()
 }
 
+// Save settings JSON to the user data directory.
 pub fn save_settings(settings: &UiSettings) -> io::Result<()> {
     let path = settings_path().ok_or_else(|| {
         io::Error::new(
@@ -30,6 +32,7 @@ pub fn save_settings(settings: &UiSettings) -> io::Result<()> {
     fs::write(path, json)
 }
 
+// Build the full path for the settings file.
 fn settings_path() -> Option<PathBuf> {
     let base = dirs::data_local_dir().or_else(dirs::data_dir)?;
     Some(base.join(APP_DIR_NAME).join(SETTINGS_FILE_NAME))