From 1d426f0b29104e972d4be31ddc6e232d4b8f4f6e Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Sat, 17 Oct 2026 18:45:17 +0100
Subject: [PATCH] Create animation

---
 src/bin/anim.rs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 src/bin/anim.rs

diff --git a/src/bin/anim.rs b/src/bin/anim.rs
new file mode 100644
index 0000000..f49012c
--- /dev/null
+++ b/src/bin/anim.rs
@@ -0,0 +1,44 @@
+use symplectic_double_pendulum::*;
+
+use macroquad::prelude::*;
+
+fn draw(dp: &DoublePendulum, fg: Color) {
+	let rod_length = 120.0;
+
+	let pivot = vec2(screen_width() / 2.0, screen_height() / 2.0);
+	let bob1 = vec2(
+		pivot.x + rod_length * (dp.theta.sin() as f32),
+		pivot.y + rod_length * (dp.theta.cos() as f32));
+	let bob2 = vec2(
+		bob1.x + rod_length * ((dp.theta + dp.phi).sin() as f32),
+		bob1.y + rod_length * ((dp.theta + dp.phi).cos() as f32));
+
+	draw_line(pivot.x, pivot.y, bob1.x, bob1.y, 2.0, fg);
+	draw_line(bob1.x, bob1.y, bob2.x, bob2.y, 2.0, fg);
+
+	draw_circle(bob1.x, bob1.y, 8.0, fg);
+	draw_circle(bob2.x, bob2.y, 8.0, fg);
+}
+
+#[macroquad::main("Double Pendulum")]
+async fn main() {
+	let omega = 500.0;
+	let h = 1e-3;
+
+	let mut state = Augmented::from(State {
+		q: DoublePendulum { theta: std::f64::consts::PI - 0.01, phi: 0.0 },
+		p: DoublePendulum { theta: 0.0, phi: 0.0 },
+	}, omega);
+
+	loop {
+		clear_background(WHITE);
+
+		let t = get_frame_time() as f64;
+		for _ in 0..((t / h) as i32) {
+			state.evolve(h);
+		}
+		draw(&state.average().q, BLACK);
+
+		next_frame().await
+	}
+}