diff --git a/crsn/src/runtime/run_thread.rs b/crsn/src/runtime/run_thread.rs
index 3c9be78..2c5dc12 100644
--- a/crsn/src/runtime/run_thread.rs
+++ b/crsn/src/runtime/run_thread.rs
@@ -48,13 +48,15 @@ impl RunThread {
         self.info.cycle_time = cycle_time;
     }
 
-    pub fn start(self) -> JoinHandle<()> {
+    /// Spawn as a thread
+    pub fn spawn(self) -> JoinHandle<()> {
         std::thread::spawn(move || {
             self.run();
         })
     }
 
-    fn run(mut self) {
+    /// Start synchronously
+    pub fn run(mut self) {
         'run: loop {
             match self.eval_op() {
                 Ok(EvalRes { cycles, advance }) => {
diff --git a/examples/mouse.csn b/examples/mouse.csn
index 355b9a4..96cebd2 100644
--- a/examples/mouse.csn
+++ b/examples/mouse.csn
@@ -1,18 +1,25 @@
 (
-    (sc-init 640 480)
+    (sc-init 800 600)
 
     (sym x r6)
     (sym y r7)
 
-    (def BOXSIZE 10)
+    (def BOXSIZE 7)
 
     (:loop)
         (sc-poll)
-        (sc-mouse x y
-            (ov? (j :next)))
+        (sc-blit 0)
+        (sc-mouse x y (ov? (j :next)))
+        (sc-mbtn _ 1 (nz? (sc-erase) (sc-blit 1)))
+        (sc-mbtn _ 0 (z? (j :next)))
 
-        (sc-mbtn r0 0 (z? (j :next)))
+        (call draw_box x y)
 
+        (:next)
+        (sleep 500)
+    (j :loop)
+
+    (proc draw_box x y
         (sym vx r0)
         (sym vy r1)
         (sym endx r2)
@@ -20,21 +27,16 @@
 
         (add endx x BOXSIZE)
         (add endy y BOXSIZE)
-
         (sub vy y BOXSIZE)
 
         (:nextline)
-        (cmp vy endy (eq? (j :endbox)))
-        (sub vx x BOXSIZE)
-        (:nextpx)
-        (sc-px vx vy 0xffffff)
-        (inc vx)
-        (cmp vx endx
-            (eq? (inc vy)(j :nextline)))
-        (j :nextpx)
-        (:endbox)
-
-        (:next)
-        (sleep 20000)
-    (j :loop)
+            (cmp vy endy (eq? (ret)))
+            (sub vx x BOXSIZE)
+            (:nextpx)
+                (sc-px vx vy 0xffffff)
+                (inc vx)
+                (cmp vx endx
+                    (eq? (inc vy)(j :nextline)))
+                (j :nextpx)
+    )
 )
diff --git a/launcher/src/main.rs b/launcher/src/main.rs
index 7beee45..95e0965 100644
--- a/launcher/src/main.rs
+++ b/launcher/src/main.rs
@@ -148,9 +148,8 @@ fn main() -> anyhow::Result<()> {
     let mut thread = RunThread::new(ThreadToken(0), None, parsed.clone(), Addr(0), args);
     thread.set_speed(config.cycle_time);
 
-    let a = thread.start();
-    // ...
-    let _ = a.join();
+    // run without spawning, so it is on the main thread - required by some extensions
+    thread.run();
 
     info!("Runtime shut down.");