diff --git a/lang-trials/rust/src/engine.rs b/lang-trials/rust/src/engine.rs
new file mode 100644
index 0000000..0dbee3f
--- /dev/null
+++ b/lang-trials/rust/src/engine.rs
@@ -0,0 +1,38 @@
+use nalgebra::*;
+
+pub struct Circle {
+  pub center_x: f64,
+  pub center_y: f64,
+  pub radius: f64,
+}
+
+// construct the circle through the points given by the columns of `points`
+pub fn circ_thru(points: Matrix2x3<f64>) -> Option<Circle> {
+    // build the matrix that maps the circle's coefficient vector to the
+    // negative of the linear part of the circle's equation, evaluated at the
+    // given points
+    let neg_lin_part = stack![2.0*points.transpose(), Vector3::repeat(1.0)];
+    
+    // find the quadrdatic part of the circle's equation, evaluated at the given
+    // points
+    let quad_part = Vector3::from_iterator(
+      points.column_iter().map(|v| v.dot(&v))
+    );
+    
+    // find the circle's coefficient vector, and from there its center and
+    // radius
+    match neg_lin_part.lu().solve(&quad_part) {
+        None => None,
+        Some(coeffs) => {
+            let center_x = coeffs[0];
+            let center_y = coeffs[1];
+            Some(Circle {
+                center_x: center_x,
+                center_y: center_y,
+                radius: (
+                    coeffs[2] + center_x*center_x + center_y*center_y
+                ).sqrt(),
+            })
+        }
+    }
+}
\ No newline at end of file
diff --git a/lang-trials/rust/src/main.rs b/lang-trials/rust/src/main.rs
index f6b97c9..af011a2 100644
--- a/lang-trials/rust/src/main.rs
+++ b/lang-trials/rust/src/main.rs
@@ -1,8 +1,8 @@
-use nalgebra::*;
+use nalgebra::Matrix2x3;
 use std::f64::consts::PI as PI;
 use sycamore::{prelude::*, rt::{JsCast, JsValue}};
 
-// --- interface ---
+mod engine;
 
 fn main() {
   // set up a config option that forwards panic messages to `console.error`
@@ -66,7 +66,7 @@ fn main() {
         // find and draw the circle through the given points
         let data_vals = data.map(|sig| sig.get()).to_vec();
         let points = Matrix2x3::from_vec(data_vals);
-        if let Some(circ) = circ_thru(points) {
+        if let Some(circ) = engine::circ_thru(points) {
           ctx.begin_path();
           ctx.set_stroke_style(&highlight_style);
           ctx.arc(
@@ -111,43 +111,4 @@ fn main() {
       }
     }
   });
-}
-
-// --- engine ---
-
-struct Circle {
-  center_x: f64,
-  center_y: f64,
-  radius: f64,
-}
-
-// construct the circle through the points given by the columns of `points`
-fn circ_thru(points: Matrix2x3<f64>) -> Option<Circle> {
-    // build the matrix that maps the circle's coefficient vector to the
-    // negative of the linear part of the circle's equation, evaluated at the
-    // given points
-    let neg_lin_part = stack![2.0*points.transpose(), Vector3::repeat(1.0)];
-    
-    // find the quadrdatic part of the circle's equation, evaluated at the given
-    // points
-    let quad_part = Vector3::from_iterator(
-      points.column_iter().map(|v| v.dot(&v))
-    );
-    
-    // find the circle's coefficient vector, and from there its center and
-    // radius
-    match neg_lin_part.lu().solve(&quad_part) {
-        None => None,
-        Some(coeffs) => {
-            let center_x = coeffs[0];
-            let center_y = coeffs[1];
-            Some(Circle {
-                center_x: center_x,
-                center_y: center_y,
-                radius: (
-                    coeffs[2] + center_x*center_x + center_y*center_y
-                ).sqrt(),
-            })
-        }
-    }
 }
\ No newline at end of file