diff --git a/src/graphics_api_impl.rs b/src/graphics_api_impl.rs
index f0f07e9..5d61e31 100644
--- a/src/graphics_api_impl.rs
+++ b/src/graphics_api_impl.rs
@@ -32,8 +32,8 @@ impl AglApi for GraphicsRenderer {
         let x2 = coords_end.x;
         let y2 = coords_end.y;
 
-        let dx = x2 - x1;
-        let dy = y2 - y1;
+        let dx = x2.wrapping_sub(x1);
+        let dy = y2.wrapping_sub(y1);
 
         for x in x1..x2 {
             let y = y1 + dy * (x - x1) / dx;
@@ -63,7 +63,9 @@ impl AglApi for GraphicsRenderer {
         thickness: u32,
         color: RGBA,
     ) {
-        todo!();
+        self.put_line(coords_1, coords_2, thickness, color);
+        self.put_line(coords_2, coords_3, thickness, color);
+        self.put_line(coords_3, coords_1, thickness, color);
     }
 
     fn paint_cursor(&mut self, coords: Point) {
diff --git a/src/main.rs b/src/main.rs
index 0bda1e5..702f0c1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -83,6 +83,20 @@ fn main() {
         },
         "Hello".to_string(),
     );
+
+    xyz.put_triangle(
+        Point { x: 10, y: 40 },
+        Point { x: 30, y: 100 },
+        Point { x: 10, y: 90 },
+        8,
+        RGBA {
+            r: 8,
+            g: 7,
+            b: 7,
+            a: 255,
+        },
+    );
+
     // update pixels
     for x in 0..600 * 400 {
         buffer[x] = [xyz.buff[x].r, xyz.buff[x].g, xyz.buff[x].b, xyz.buff[x].a]