DOCS

The single best free document on the genre: play area, movement, bullet visibility, the three pattern types, lanes, enemy roles, the Toaplan pattern, wave overlap, pacing, scoring. CAVE-skewed, broadly applicable.

The same document in its original form.

Engine-independent danmaku theory with live interactive canvases. The academic complement to Boghog.

The vocabulary the rest of these resources assume you already have.

What the series covers and how to read it.

Bullet components, spawners, spawn rate against speed.

Directed bullets, angle usage, and how players mentally filter a screen.

Subpatterns and N-way / N-stack notation.

Micro against macrododging, spatial against temporal density, negative space.

Free, open source; strong 2D pipeline and bullet-friendly scene system.

The engine behind many commercial shmups.

Fast 2D iteration; shipped Crimzon Clover and countless doujin shooters.

Minimal Lua framework, good for jams and bullet experiments.

No-code 2D/3D builder with a pattern editor, scoring, medals and chaining. Paid, active Discord. Also on Steam.

Kenta Cho's XML language for describing barrages; ports exist for most engines.

A maintained reader if you are working in C#.

A Haxe DSL for defining 2D bullet patterns.

Lightweight JS and Canvas danmaku engine, made for prototyping and for embedding live pattern demos in a web page.

Unreal Engine toolkit, data-table driven, no actor editing.

Browser tool: aimed, static, random, spiral, wave and circle.

The scripting course for Danmakufu, the Touhou community engine. Also available in Spanish.

The most feature-packed bullet hell plugin for Godot 3 and 4, actively maintained.

MultiMeshInstance2D and a C++ GDExtension: thousands of bullets at speed.

GPU-instanced projectile generator.

Open source danmaku development kit.

A full bullet hell engine with its own declarative scripting language. MIT.

Bullet hell library for GameMaker Studio 2.3 and later.

Actively developed fork of the LuaSTG engine.

Particle-system bullets for 3D shooters.

Everything else, browsable and current.

The whole open-source catalogue: Noiz2sa, Torus Trooper, Tumiki Fighters, Parsec 47, Gunroar.

Cho's BulletML showcase: procedurally generated barrages across 120 stages.

A complete bullet hell in under 100 KB of C++, built from scratch.

Console danmaku in C, written in about four hours. The core loop stripped bare.

HTML5 and p5.js, and very readable.

A shoot-em-up in Rust and Bevy.

A horizontal Touhou fangame in C#.

Godot stress test: how many enemies can you actually run?

Curated multilingual index of the Touhou development and tooling ecosystem.

An early experiment in procedural boss pattern generation.

Himeki Games on level and wave flow.

Popcorn enemies, bomb design, bullet differentiation.

The developer on bullets, level design, and selling the thing.

Bagoum on expressing patterns as a language.

A taxonomy: radial, spiral, fan, ring, floral, grid, rain, laser. Japanese, with an English toggle.

Community-written PDF pack. Free.

On a boss that rebuilds itself around how you beat it.

Written tutorial with real code: sprite sheet, bullet class, patterns, rendering.

Khalifa, Lee, Nealen, Togelius (GECCO 2018). A description language for bullet hell levels, evolved along strategy and dexterity. The foundational paper.

Danmaku as parametric sequences; TimeGAN against a periodic spatial GAN.

Survey placing bullet hell generation in the wider MAP-Elites landscape.

Isaksen, Gopstein, Nealen (FDG 2015). Difficulty by Monte Carlo simulation and a motor-skill player model. The rigorous version of "how hard is my game".

The extended journal version, IEEE ToG 10(2), 2018.

Everything else from the same group.

Translated Japanese developer interviews: CAVE, Toaplan, doujin developers. Enormous and underused.

One example of what is in there.

Danbo on Electric Underground.

Long-form history and analysis.

Verified world records. Useful for seeing where the ceiling actually is.

Batsugun and Toaplan, and how the term arrived.

The author of the 101 document, in conversation.

Mechanical analysis and developer interviews.

The interview playlist.

One game per episode, in depth.

Superplays. The clearest way to see intended routing.

Multi-part build-along, starting with collisions.

Where the same series reaches enemy spawners.

Movement, then patterns, then enemies, on a finite state machine.

Another full playlist.

Microguide by Yokcos, developer of Fishticuffs.

The GameMaker equivalent.

General GameMaker and Godot teaching. No shmup series, but the fundamentals are here.

The genre's centre of gravity, and decades deep.

Devlogs and engine talk.

A long-running link roundup on that forum.

The thread where Boghog gets recommended, and why.

Practical thread on Catmull splines for paths and frame-triggered firing.

Channels per engine, plus design theory, art and music.

Danmakufu's home. The development board is Rika and Nitori's Garage Experiments.

The wiki community.

The classic thread on timeline JSON against spatial-trigger wave spawning, with pseudocode.

The standard pixel-art and animation editor.

Free ship sprites, bullets and explosion sheets to prototype with.

Ships, bullets, explosions, vertical backgrounds. Much of it free.

The same, narrowed to GameMaker.

NES-style music tracker for authentic 8-bit soundtracks.

Multi-chip tracker: YM2612, SN76489 and other arcade-era sound.