Last Bastion

A ten-level tower defense game for the browser, built by parallel Claude Code agents with arbab and rendered with the ExodeUI runtime.

▶ Play it in your browser

Goblins, trolls, bats and shield orcs march down the road toward your castle. Build towers on the stone pads, upgrade them, and hold the gate until the last wave falls. Every enemy that gets through costs lives; at zero, the castle is lost.

• 10 levels on four maps (meadow, desert, snow, volcano), with one to three roads.
• 5 towers, three upgrade levels each: Rifleman, Cannon, Frost Tower, Tesla Coil and Rocket Launcher.
• 6 enemy types: Goblin, Runner, Troll, Bat, Shield Orc and the Orc Warlord boss.
• 3 difficulties: easy (25 lives), normal (20) and hard (10, with tougher, faster enemies and less gold).
• Stars and saved progress: up to three stars per level and difficulty from the lives you keep, saved in your browser.
• King Sunny, the lion king of the bastion, cheers you on and worries when the gate is in danger.

Meadow	Desert
Snow	Volcano

How to play

Action	Mouse	Keyboard
Build a tower	Click an empty stone pad, then a tower	1–5 while the build menu is open
Upgrade or sell	Click a tower, then upgrade or sell	U / S while the tower menu is open
Start the first wave	START
Call the next wave early	NEXT (+1 gold for every second skipped)
Pause	Pause button	Space or Esc
Double speed	Speed button	F
Sound on or off	Sound button	M

Rifles, cannons and rockets deal physical damage, which armor reduces and shields halve; frost and tesla deal energy damage, which ignores both. Cannons cannot hit flyers, rockets hit them extra hard, frost shards slow what they hit and tesla bolts chain between enemies. The Orc Warlord costs 10 lives if he reaches the gate.

How it was built

The game was built with arbab, a Claude Code plugin that turns one Claude Code session into an engineering team: the session plans and writes narrow briefs, and arbab runs each brief as a headless Claude Code worker, in parallel, in its own git worktree behind a sandbox.

                                  ┌─> lane ─┐
orchestrator session + arbab ─────┼─> lane ─┼─> integrate ─> verify ─> review ─> readiness ─> person approves ─> main
(contracts, briefs, integration)  └─> lane ─┘

1. Contracts first. The orchestrator, an interactive Claude Code session, studied the ExodeUI runtime and wrote the shared ground every lane builds on: game types and stat tables, SpriteBuilder (a typed builder for ExodeUI artboards), the stage and engine helpers, and a Node render pipeline so tests and galleries can draw real frames.
2. Lanes in waves. Each lane got a brief with a fixed scope, decided facts and acceptance checks. Simulation, levels and art ran in parallel; then the world scene, HUD, menus and difficulty tuning; then the app shell, the engine effects and the mascot; last, the showcase (SEO, icons, media and the Pages deploy).
3. Gates before main. Every wave was integrated, then verified inside the sandbox (typecheck, the full test suite and the production build), reviewed for correctness, performance and security with a skeptic pass that tries to refute each finding, and checked for readiness. Confirmed findings went back to a lane with a test that fails without the fix. Nothing reached main until a person said yes.

The workers looked at their own work. Art lanes rendered every sprite, clip and variant to PNG with pnpm art:render and iterated on what they saw; the tuning lane played every level on every difficulty with a headless bot (60 plays in about 3 seconds, see src/game/balance).

Cost and time

Area	What it covers	Time	Cost
Orchestrator	Plan, shared contracts, lane briefs, integration, browser captures, this README	2 h 13 min	$90.30
Simulation	Deterministic 60 Hz simulation, economy, waves, a headless balance bot	23 min	$6.50
Levels	The ten level definitions and their validation	17 min	$4.71
Difficulty tuning	Waves and starting gold tuned with the bot on every level and difficulty	29 min	$8.43
Tower art	Five towers at three levels, with aim and fire clips	29 min	$8.16
Enemy art	Six enemies with walk, hit and die clips	21 min	$5.54
World art	Terrain for four themes, decor, castle gates, projectiles and impact effects	25 min	$8.49
UI kit	Buttons, panels, icons, tags, range rings, hit testing	14 min	$4.00
HUD	In-game HUD, build and tower menus, wave banner, overlays	17 min	$5.35
Menus	Title screen, level select with difficulty	13 min	$4.53
World scene	Rendering adapter: terrain layer, pooled towers, enemies, projectiles and effects	32 min	$9.14
Engine effects	ExodeUI glows, light trails and particle emitters in the scene	34 min	$11.74
Mascot	King Sunny's reactions to the game, screen shake	26 min	$10.39
App shell	Screens, game loop, input, procedural audio, saved progress	12 min	$3.32

• Elapsed working time: 6 h 16 min. Lanes ran in parallel, so the work above fit into 6 h 16 min during which at least one agent was working.
• Lanes: 18 building lanes, 15 reviewer and skeptic lanes, and 6 verification and preflight lanes.
• Time is measured working time: lane run time from arbab's run records, and for the orchestrator, model and tool time from its session log. Time spent waiting for a person, for a usage-limit reset or with nothing running is not counted.
• Cost is API-equivalent: what the tokens cost at Claude API prices. For lanes it is the cost Claude Code reports for each run; for the orchestrator it is the session's logged token usage at Claude Opus 5.5 rates ($4 / $20 per million input / output tokens, $8 per million for one-hour cache writes, $0.20 per million for cache reads).
• Models: the orchestrator and every building and reviewing lane ran Claude Opus 5.5 (lanes at high effort); verification ran on Claude Haiku 5.5.

How ExodeUI is used

ExodeUI is an interactive animation and UI runtime, a Rive alternative. Here its canvas engine draws the whole game: every sprite, map, projectile, effect, HUD element and menu is an ExodeUI artboard, and the mascot is ExodeUI's own mascot component.

• Art as code. Artboards are built in TypeScript with SpriteBuilder (src/art/exode.ts): shapes, Bézier paths, linear and radial gradients from a shared palette, outlined text and keyframe clips with easing. Builders are pure (objects in, artboard out), so every sprite is unit-tested and rendered to PNG in Node.
• Engine-driven scene. The engine's object list is fixed when an artboard loads, so enemies, projectiles and effects are pools of hidden instances. Each frame the scene adapter (src/render/scene) writes positions, rotations, opacity, visibility and text from the simulation's view, and replays baked clips: walk cycles, recoil, hits and deaths.
• Built-in effects. Outer Glow on tesla spheres, frost crystals, lightning and explosions; LightTrail behind rockets, ice shards and cannonballs; ParticleEmitter sparks, debris, ice motes and volcano embers on a second, small engine over the world canvas. Their cost was measured per instance, and an adaptive guard turns them off when a device cannot keep its frame pace (ENGINE_EFFECTS.md).
• King Sunny. ExodeUI's rigged Sunny the Lion (ip-2011) from its mascot library, recolored gold, crimson and royal blue through the <exode-mascot> web component. He greets you on the menus, pops up during a level when the first wave starts, a boss arrives, the gate is in danger or you clear waves without a leak, and celebrates or cries with you at the end.
• What we learned about the runtime is written down where the agents read it: the ExodeUI facts in CLAUDE.md (transforms, paths, text, clips, layers, what not to use and why) and the measured effect costs in ENGINE_EFFECTS.md.

Towers at levels 1, 2 and 3	Enemies

Project layout

Path	What
src/game	Shared types and stat tables, the deterministic simulation, the ten levels, balance tests. No DOM, no rendering
src/art	ExodeUI artboard builders: towers, enemies, world, UI kit, and the SpriteBuilder toolkit
src/render	Canvas stage, engine helpers and the world scene adapter
src/ui	HUD and menus
src/app	App shell: screens, loop, input, audio, storage, mascot, quality guard
src/platform	Node canvas rendering for tests and galleries
scripts	Gallery renderer, media renderer, SEO and media tests

The simulation runs at a fixed 60 Hz step with no randomness or clock reads, so a level plays out the same way every time; the balance tests rely on that. The project has 135 TypeScript source files, 10 art galleries and 110 test files with 879 tests.

Run it locally

Requires Node 24 and pnpm 12.

pnpm install
pnpm dev                 # play at http://localhost:5173
pnpm test                # unit, render and balance tests
pnpm typecheck
pnpm build               # production build in dist/
pnpm art:render [filter] # render gallery entries to out/renders/*.png
pnpm media               # render the icons and the Node-side README media

FAQ

What is Last Bastion? A free tower defense game that runs in the browser: ten levels on four themed maps, five towers with three upgrade levels each, six enemy types including the Orc Warlord boss, and three difficulties.

How was it built? With arbab: a Claude Code session wrote the shared contracts and the briefs, and arbab ran each part (simulation, levels, art, scene, HUD, menus, tuning, app shell, effects, mascot) as a headless Claude Code worker in its own git worktree. Verification, code review and a person's approval gated every merge.

What is ExodeUI? An interactive animation and UI runtime, a Rive alternative. Every sprite, map, effect and menu here is an ExodeUI artboard drawn by its canvas engine, and King Sunny comes from ExodeUI's mascot library.

How much did it cost and how long did it take? 10 h 15 min of measured agent work and $221.71 at API prices, within 6 h 16 min of elapsed working time. The cost table breaks it down by area.

Can I use the code? Yes, under the MIT license. The font and the mascot have their own terms, listed below.

Third-party code and assets

• ExodeUI runtime: the exodeui npm package, pinned at 7.2.18 and bundled into the build.
• The mascot component is ExodeUI's official embed, loaded at runtime from https://www.exodeui.com/mascots/exode-mascot.js; its license is not stated, so it is not redistributed here. It runs with this page's privileges and cannot be pinned with Subresource Integrity, because exodeui.com sends no CORS headers. The page keeps only game progress and settings in localStorage, but a GitHub Pages project site shares its origin, and so its storage, with the owner's other project sites. If the script does not load, the game runs without the mascot (src/app/mascot.ts).
• The mascot art (public/mascots/ip-2011.bexode, Sunny the Lion) comes from ExodeUI's mascot library, free for personal and commercial use. It is served from this site because the component cannot fetch it from exodeui.com across origins.
• Lilita One font (public/fonts), under the SIL Open Font License (OFL.txt).

License

MIT © 2026 Özgür Sağıroğlu.