start from 0 works

src/main.rs

@@ -60,19 +60,23 @@ fn main() {
     let env = init_env();
 
     let mut ball = Projectile::new(
-        Tuple::point(0.0, 0.0, 1.0),
+        Tuple::point(0.0, 0.0, 0.0),
         Tuple::vector(2.2, 0.0, 21.0),
     );
 
     let mut canvas = Canvas::new(300, 300);
     let color = Color::new(1.0, 1.0, 0.0);
-    while ball.position.z() < canvas.height() as f32
-        && ball.position.z() >= 0.0
-        && ball.position.x() < canvas.width() as f32
-        && ball.position.x() >= 0.0 {
-        canvas.write_pixel(ball.position.x() as usize, canvas.height() - ball.position.z() as usize, color);
+    loop {
+        canvas.write_pixel(ball.position.x() as usize, canvas.height() - (ball.position.z() as usize) - 1, color);
 
         ball.tick(&env);
+        println!("ball {}", ball);
+        if ball.position.z() >= (canvas.height() - 1) as f32
+        || ball.position.z() < 0.0
+        || ball.position.x() >= (canvas.width() - 1) as f32
+        || ball.position.x() < 0.0 {
+            break;
+        }
     }
 
     let ppm = canvas.to_ppm();