When running:

```bash
cargo run --example yinyang --features svg -- --export-svg yinyang.svg
```
the application crashed with:
```text
thread 'main' panicked at macroquad-0.4.16/src/lib.rs:172:13:
assertion failed: THREAD_ID.is_some()
```
along with 10 compiler dead-code warnings in `turtle-lib`.

1. **Headless Execution Path**: When `--export-svg` is provided,
   `turtle_main` runs `run_headless_svg_export` headlessly without
   creating a graphics window (`macroquad::Window::new` is bypassed).
2. **Speed Overwrite in Headless Mode**: `run_headless_svg_export`
   originally called `app.set_all_turtles_speed(Instant(1000))` and
   stepped animations with `while !app.is_complete() {
   app.step_animations(); }`. However, `yinyang.rs` contains
   `turtle.set_speed(100)` in its plan. When `TweenController` processed
   `SetSpeed(100)`, it switched to animated mode.
3. **Macroquad Context Assertion**: In animated mode,
   `TweenController::update` creates a `CommandTween` and called
   `current_time()`. In `turtle-lib/src/tweening.rs`, `current_time()`
   called `macroquad::time::get_time()`, which queried Macroquad's
   context (`get_context()`). Because no window was created, Macroquad
   asserted `THREAD_ID.is_some()` and panicked.
4. **Dead Code Warnings**: Types previously made `pub(crate)` had dead
   fields and obsolete helper methods that were never called internally
   or were superseded by `execution.rs`.

---

-
  **[`turtle-lib/src/export.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/export.rs)**:
  - Updated `run_headless_svg_export` to use `app.execute_immediate(0,
    turtle)` instead of queuing commands and stepping animations in a
    loop.
  - Headless SVG export now executes all commands synchronously in under
    0.1s regardless of any `set_speed` in the drawing plan.
-
  **[`turtle-lib/src/lib.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/lib.rs)**:
  - In `TurtleApp::execute_immediate`: ensured the turtle exists in
    `self.world` before executing.
  - Removed unused `pub(crate) fn world` and `pub(crate) fn world_mut`.
-
  **[`turtle-lib/src/tweening.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/tweening.rs)**:
  - Updated `current_time()` to use monotonic `std::time::Instant` on
    non-WASM targets (`#[cfg(not(target_arch = "wasm32"))]`) and
    `macroquad::time::get_time()` on WASM (`#[cfg(target_arch =
    "wasm32")]`).
  - Removed unused `turtle_id` field on `CommandTween`.

-
  **[`turtle-lib/src/circle_geometry.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/circle_geometry.rs)**:
  - Removed obsolete unused methods: `position_at_progress`,
    `angle_to_position`, `draw_arc_params`, and
    `draw_arc_params_partial`.
-
  **[`turtle-lib/src/commands_channel.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/commands_channel.rs)**:
  - Removed unused `turtle_id` field from `TurtleCommandReceiver`.
  - Removed unused methods `turtle_id`, `try_recv`, `is_empty`, and
    `len` from `TurtleCommandReceiver`.
-
  **[`turtle-lib/src/general.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/general.rs)**:
  - Removed unused `Visibility` type alias.
-
  **[`turtle-lib/src/state.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/state.rs)**
  &
  **[`turtle-lib/src/execution.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/execution.rs)**:
  - Removed unused `start_position` field on `FillState`.
  - Removed unused superseded methods on `Turtle`: `heading_angle`,
    `reset`, `begin_fill`, `record_fill_vertex`, `close_fill_contour`,
    `start_fill_contour`, `record_fill_vertices_for_arc`, `reset_fill`.
  - Removed unused `background_color` field and unused methods
    `get_turtle`, `reset_turtle`, `clear` from `TurtleWorld`.
  - Added `#[allow(clippy::struct_field_names)]` on `Turtle::turtle_id`.
-
  **[`turtle-lib/src/export_svg.rs`](file:///home/dietrich/Projekte/Source/turtlers/turtle-lib/src/export_svg.rs)**:
  - Moved `update_bounds` outside `export`.
  - Replaced `if angle.value() > 180.0 { 1 } else { 0 }` with
    `i32::from(angle.value() > 180.0)`.
  - Replaced `d.push_str(&format!(...))` with `write!(d, ...)`.
  - Inlined format arguments in `color_to_svg`.

---

```bash
cargo run --example yinyang --features svg -- --export-svg yinyang.svg
```
Output:
```text
Finished `dev` profile [optimized + debuginfo] target(s) in 0.07s
Running `target/debug/examples/yinyang --export-svg yinyang.svg`
SVG exported successfully to: yinyang.svg
```
Completed cleanly in **0.07s** with **0 compiler warnings** and **0
errors**.

Inspected `yinyang.svg`: contains all expected paths, outer arcs, inner
S-curve, and EvenOdd fill contours.

```bash
cargo test --package turtle-lib --features svg
```
Output:
```text
test result: ok. 16 passed; 0 failed; 0 ignored; 0 measured; 0 filtered
out; finished in 0.00s
test result: ok. 34 passed; 0 failed; 1 ignored; 0 measured; 0 filtered
out; finished in 0.25s
```

```bash
cargo clippy --package turtle-lib --features svg -- -Wclippy::pedantic \
-Aclippy::cast_precision_loss -Aclippy::cast_sign_loss
-Aclippy::cast_possible_truncation
```
Output:
```text
Checking turtle-lib v0.2.0
(/home/dietrich/Projekte/Source/turtlers/turtle-lib)
Finished `dev` profile [optimized + debuginfo] target(s) in 0.51s
```
**0 warnings.**

turtle-lib/src/tweening.rs

@@ -54,7 +54,6 @@ pub(crate) struct TweenController {
 
 #[derive(Clone, Debug)]
 pub(crate) struct CommandTween {
-    pub(crate) turtle_id: usize,
     pub(crate) command: TurtleCommand,
     pub(crate) start_time: f64,
     pub(crate) duration: f64,
@@ -316,7 +315,6 @@ impl TweenController {
             );
 
             self.current_tween = Some(CommandTween {
-                turtle_id,
                 command,
                 start_time: current_time(),
                 duration,
@@ -396,14 +394,14 @@ pub(crate) fn normalize_angle(angle: f32) -> f32 {
 
 #[inline]
 fn current_time() -> f64 {
-    #[cfg(test)]
+    #[cfg(not(target_arch = "wasm32"))]
     {
         use std::sync::OnceLock;
         use std::time::Instant;
         static START: OnceLock<Instant> = OnceLock::new();
         START.get_or_init(Instant::now).elapsed().as_secs_f64()
     }
-    #[cfg(not(test))]
+    #[cfg(target_arch = "wasm32")]
     {
         macroquad::time::get_time()
     }