start dev mode only when run with cargo. remove "mute_music" feature

Cargo.toml

@@ -47,9 +47,8 @@ embed-resource = "1.6.3"  # embedding of .exe metadata
 
 [features]
 default = ["x11", "embed_assets"]
-mute_music = []
 dev_mode = []
-dev = ["dev_mode", "mute_music", "bevy/dynamic_linking", "bevy/file_watcher"]
+dev = ["dev_mode", "bevy/dynamic_linking", "bevy/file_watcher"]
 release_linux = ["x11", "wayland", "embed_assets"]
 release_windows = ["embed_assets"]
 wasm = ["bevy/webgl2"]

HACKING.md

@@ -6,7 +6,7 @@ For development, it's recommended to use `--features dev`:
 cargo [run|build] --features dev
 ```
 
-This enables the following:
+This enables the following, but ONLY if you run it with `cargo run`:
 
 - Mutes music by default (you can still unmute it)
 - Enables "dev mode", which changes the game slightly:

src/var.rs

@@ -128,9 +128,9 @@ pub struct Settings {
 
 impl Default for Settings {
     fn default() -> Self {
-        let dev_mode = cfg!(feature = "dev_mode");
+        let dev_mode = cfg!(feature = "dev_mode") && env::var("CARGO").is_ok();
         let default_mute_sfx = false;
-        let default_mute_music = cfg!(feature = "mute_music");
+        let default_mute_music = dev_mode;
         let version = if let Some(version) = option_env!("CARGO_PKG_VERSION") {
             version.to_string()
         } else {