Piston Sudoku up through 3rd chapter

piston-tutorials/sudoku/Cargo.toml

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+[package]
+name = "sudoku"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+piston = "0.53.2"
+piston2d-graphics = "0.43.0"
+piston2d-opengl_graphics = "0.82.0"
+pistoncore-glutin_window = "0.70.1"

piston-tutorials/sudoku/src/main.rs

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+#![deny(missing_docs)]
+
+//! An Sudoko please.
+
+extern crate glutin_window;
+
+use glutin_window::GlutinWindow;
+use opengl_graphics::{GlGraphics, OpenGL};
+use piston::event_loop::{EventSettings, Events};
+use piston::{EventLoop, RenderEvent, WindowSettings};
+
+fn main() {
+    let opengl = OpenGL::V3_2;
+    let settings = WindowSettings::new("Sudoku", (640, 480))
+        .exit_on_esc(true)
+        .graphics_api(opengl)
+        .vsync(true);
+    let mut window: GlutinWindow = settings.build().expect("could not create window");
+    let mut events = Events::new(EventSettings::new().lazy(true));
+    let mut gl = GlGraphics::new(opengl);
+
+    while let Some(e) = events.next(&mut window) {
+        if let Some(args) = e.render_args() {
+            gl.draw(args.viewport(), |c, g| {
+                use graphics::clear;
+
+                clear([1.0; 4], g);
+            })
+        }
+    }
+}