New Flappy Bird example #19282

tertsdiepraam · 2025-05-18T20:24:13Z

Hi!

Objective

This adds a new example to the repository implementing Flappy Bird, as was suggested during the RustWeek unconf. As far as I understand, the goal is to add another example implementing a "full" game, combining multiple Bevy features.

Solution

This is a simplified implementation of Flappy Bird using the logo as the titular bird and simply using black rectangles as pipes. It features a scoring mechanism and resets on collision. Since this is an example, I tried to document even the more obvious parts.

While I've used Bevy a bit before, I do not have a very good idea of what idiomatic Bevy code looks like. I would appreciate any feedback there.

Missing from this implementation are:

Prettier artwork
Background music
~~A menu screen~~
~~A game over screen~~
A good way of handling window resizing

Testing

I tested this on my own machine. One thing that probably needs some tweaking is handling of other window sizes and resizing as the game is largely tailored to a particular screen size.

cargo run --example flappy_bird

Showcase

This is what it looks like:

github-actions · 2025-05-18T20:24:25Z

Welcome, new contributor!

Please make sure you've read our contributing guide and we look forward to reviewing your pull request shortly ✨

bushrat011899 · 2025-05-18T23:30:24Z

Cargo.toml

@@ -4361,3 +4361,14 @@ name = "Extended Bindless Material"
 description = "Demonstrates bindless `ExtendedMaterial`"
 category = "Shaders"
 wasm = false
+
+[[example]]
+name = "flappy_bird"


Nit: Should we choose a name other than "Flappy Bird"? I would assume the name is trademarked, and unlike "Breakout", it's reasonably recent.

You are probably right. I'll think about a nice bevy-inspired name!

Fun fact: apparently there is a whole thing around the copyright of Flappy Bird. Some crypto bros did a Flappy Bird thing and then the original creator got mad. There's also some people claiming the original Flappy Bird infringes on Nintendo copyright.

Quick search for Floppy Bevy led me to https://github.com/rust-adventure/floppy-corgi haha...

bushrat011899 · 2025-05-18T23:42:59Z

examples/games/flappy_bird.rs

+const BACKGROUND_COLOR: Color = Color::srgb(0.9, 0.9, 0.9);
+
+/// Timer spawning a pipe each time it finishes
+const PIPE_TIMER_DURATION: Duration = Duration::from_millis(2000);
+
+/// Movement speed of the pipes
+const PIPE_SPEED: f32 = 200.;
+
+/// The size of each pipe rectangle
+const PIPE_SIZE: Vec2 = Vec2::new(100., 500.);
+
+/// How large the gap is between the pipes
+const GAP_HEIGHT: f32 = 300.;
+
+/// Gravity applied to the bird
+const GRAVITY: f32 = 700.;
+
+/// Size of the bird sprite
+const BIRD_SIZE: f32 = 100.;
+
+/// Acceleration the bird is set to on a flap
+const FLAP_POWER: f32 = 400.;
+
+/// Horizontal position of the bird
+const BIRD_POSITION: f32 = -500.;


Controversial Nit: This is consistent with our other examples, but I'm not a fan of these hard-coded constants. They're all-caps and I don't believe particularly good practice (these kinds of settings would normally be controlled in a configuration file read by the build system for example). I think it would be nicer if all of this was wrapped in a Settings resource (ideally implementing Reflect for runtime configuration...), with these values being in the Default implementation.

That would be so good with this RFC: https://github.com/rust-lang/rfcs/blob/master/text/3681-default-field-values.md. I'll give your suggestion a go.

bushrat011899 · 2025-05-19T00:08:19Z

examples/games/flappy_bird.rs

+const BIRD_POSITION: f32 = -500.;
+
+#[derive(Component)]
+struct Bird;


Super tiny nit: I believe we refer to the Bevy bird as birb in the examples, might be nice to be consistent here, even if it is a little silly.

bushrat011899 · 2025-05-19T00:09:18Z

examples/games/flappy_bird.rs

+) {
+    commands.spawn(Camera2d);
+
+    let score_sound = asset_server.load("sounds/breakout_collision.ogg");


Suggested change

let score_sound = asset_server.load("sounds/breakout_collision.ogg");

// TODO: Replace with a specific sound, or rename file

let score_sound = asset_server.load("sounds/breakout_collision.ogg");

bushrat011899 · 2025-05-19T00:13:26Z

examples/games/flappy_bird.rs

+    for ent in bird {
+        commands.entity(ent).despawn();
+    }
+
+    for ent in pipes {
+        commands.entity(ent).despawn();
+    }
+
+    for ent in pipe_markers {
+        commands.entity(ent).despawn();
+    }


Future PR: Surprised we don't have a Commands::despawn_batch to make this cleaner! Might be nice to create a new EntityBatchCommands (similar to EntityCommands) for operations which could be applied to many entities, just as a quality-of-life improvement.

commands.batch([e1, e2, e3]).despawn();

cart once said something about a despawn_batch: #2693 (comment)

It seems to be valid today in principle.

I'll make it slightly cleaner by combining all the entities in a single query. Then at least it just becomes one for loop.

bushrat011899 · 2025-05-19T00:14:28Z

examples/games/flappy_bird.rs

+    for mut text in score_text {
+        text.0 = 0.to_string();
+    }


Nit: We expect a single entity to exist with the ScoreText component. That query should be changed to Single<> and this for loop removed.

bushrat011899 · 2025-05-19T00:17:07Z

examples/games/flappy_bird.rs

+#[derive(Component)]
+struct Pipe;
+
+#[derive(Component)]
+struct PipeMarker;


Nit: Might be nice to use required-components to ensure these are added together. Likewise for Score and ScoreText.

I don't think required components are correct here. At least as far as I understand required components. The pipes are represented with 1 marker and 2 pipes, so there isn't really a 1-1 requirement. For the scoring part, the Score is a resource, not a component, so I'm not sure that works either?

I might be totally off here, please correct me if I'm wrong.

rparrett · 2025-05-19T00:53:31Z

I wonder a bit about using flappy bird specifically as an example. There's just a great deal of overlap in what this is demonstrating and what we already have in breakout.

tertsdiepraam · 2025-05-19T07:16:52Z

I was wondering about that too. One solution to that would be to, for example, to put more emphasis on sprites and adding menus. Then this might become different enough to merit another example.

tertsdiepraam · 2025-05-19T12:45:30Z

I added some menus to see how complex that would make it. I'm not sure whether that makes it better as an example. As far as I can see there is no example that features both a menu and a game, but it's also not too hard to infer. Anyway, I'm having fun learning those parts of bevy (also this is my first time using states, so ideas on how to make it cleaner are very welcome).

I can revert this commit if a more trimmed down version is preferred. I guess it comes down to what the goal of this example would be. Either we keep it very small (possibly stepping on the toes of breakout) or it's more complex (possibly too complex). Opinions welcome!

add initial implementation of the Flappy Bird example

6e4a60f

tertsdiepraam force-pushed the flappy-bird branch from 839f771 to 6e4a60f Compare May 18, 2025 20:32

tertsdiepraam changed the title ~~Add initial implementation of the Flappy Bird example~~ New Flappy Bird example May 18, 2025

bushrat011899 reviewed May 19, 2025

View reviewed changes

bushrat011899 added C-Examples An addition or correction to our examples A-Meta About the project itself D-Modest A "normal" level of difficulty; suitable for simple features or challenging fixes S-Needs-Review Needs reviewer attention (from anyone!) to move forward labels May 19, 2025

tertsdiepraam added 3 commits May 19, 2025 12:52

adapt Flappy Bird example to review comments

216205a

introduce a Settings struct to the Flappy Bird example

c1f3668

add menus to the flappy bird example

da63a76

tertsdiepraam marked this pull request as draft May 19, 2025 12:49

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New Flappy Bird example #19282

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tertsdiepraam commented May 18, 2025 •

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tertsdiepraam commented May 19, 2025

	let score_sound = asset_server.load("sounds/breakout_collision.ogg");
	// TODO: Replace with a specific sound, or rename file
	let score_sound = asset_server.load("sounds/breakout_collision.ogg");

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tertsdiepraam commented May 18, 2025 • edited Loading

Objective

Solution

Testing

Showcase

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rparrett commented May 19, 2025

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