engine structure

examples/cube.rs

@@ -8,12 +8,10 @@ fn main() {
     engine.thread("Main.tick", || {});
 
     let my_rect = engine.entity(|r| {
-        r.draw_rect(8, 3, 11, 5, 0x0000ff);
+        r.draw_rect(0, 0, 2, 1, 0x0000ff);
     });
 
-    terminal::clear().unwrap();
-
-    my_rect.render(&mut osmium::renderer::Renderer {});
+    engine.start();
 
     terminal::show_cursor().unwrap();
 }