A browser-based technology research probability calculator for Stellaris. Configure your empire's modifiers, DLC, civics, and traditions to see exactly how they affect research weights, draw probabilities, and opportunity costs for all 663 technologies.

Live Demo →

• Interactive tech tree — zoomable, pannable dependency graph with canvas-rendered bezier edges, area-split layout (Physics/Society/Engineering as separate sub-trees with colored separators), chain highlighting on selection, and blueprint grid background
• 663 technologies with accurate weight calculations matching the game's logic
• Monte Carlo simulation for draw probabilities, offloaded to Web Workers for a responsive UI
• Full empire configuration — DLC toggles, civics, traditions, ascension perks, ethics, origins, game year, and more (416 atomic facts + 17 scalar sliders)
• Expertise & council — per-category expertise levels and councillor position modifiers
• Tech swaps — 126 conditional technology replacements evaluated in real time
• Delta weights — see the opportunity cost of researching each tech
• Tech View presets & filters — 5 presets (Current, Current + Past, Potential, Not Possible, All) with 7 individual filters that can be toggled independently. Presets are shortcuts that set filter combinations; manual tweaks auto-deselect the preset
• Search, filter & sort — find techs by name, filter by area (Physics/Society/Engineering), sort by 8 criteria: hit chance, weight, name, tier, delta, base weight, category, or area
• Zoom controls — adjust tech card size (60%–140%), persisted across sessions
• Save game import — drag-and-drop a Stellaris .sav file to auto-configure the calculator. Extracts DLCs, ethics, civics, origin, traditions, ascension perks, researched techs, council leaders (including ruler for gestalt empires), starbases, deposits, districts, buildings, megastructures, species traits, resources, crisis progression, completed dig sites, precursor event chains, graphical culture, nebula presence, and more. A detailed import log shows exactly what was detected
• Save/Load — persist empire configurations to localStorage or export/import as JSON
• Tutorial overlay — built-in guide for new users, auto-shown on first visit
• Self-contained — all data and 800+ AVIF icons ship with the app. No Stellaris installation needed. Version tracking shows app + Stellaris version in the sidebar footer
• ~172 KB gzipped JavaScript bundle (+ 8 KB CSS)

# Install dependencies npm install # Start dev server npm run dev # Build for production npm run build # Preview production build locally npm run preview

Push to the main branch and the GitHub Actions workflow handles everything:

1. Go to Settings → Pages → Source and select GitHub Actions
2. Push to main — the workflow builds and deploys automatically

npm run deploy

This runs gh-pages -d dist to push the built files to the gh-pages branch.

Override the base path for non-GitHub-Pages deployments:

VITE_BASE=/ npm run build # or npm run build:local

src/ ├── data/ # JSON game data (editable for Stellaris patches) │ ├── technologies.json # 663 techs │ ├── atomic_facts.json # 416 boolean flags │ └── ... # 5 more data files │ ├── types/ # TypeScript interfaces ├── state/ # Reactive stores (SolidJS signals/stores) │ ├── dataStore.ts # Loads & indexes all JSON data │ ├── empireState.ts # Empire modifiers (facts, scalars, expertise) │ └── techState.ts # Per-tech runtime state (weight, hit%, etc.) │ ├── engine/ # Calculation logic (pure functions) │ ├── logicEvaluator.ts # AND/OR/NOT/NOR boolean tree evaluator │ ├── weightCalculator.ts # Weight formula with modifier chain │ ├── inlineScripts.ts # Rare tech, archaeotech, cosmic storms │ ├── techSwaps.ts # Conditional tech swap evaluator │ ├── treeLayout.ts # Sugiyama-style tree layout (area-split, barycentric) │ └── updateCascade.ts # 8-step pipeline orchestrator │ ├── workers/ # Web Worker (Monte Carlo simulation) │ ├── monteCarloWorker.ts # Prefix sums, binary search, convergence │ └── workerApi.ts # Comlink wrapper │ ├── components/ │ ├── layout/ # App shell (Sidebar, Toolbar) │ ├── empire/ # Empire modifier controls │ ├── tech/ # Tech cards, grid, summary │ ├── tree/ # Interactive tech tree (canvas edges, nodes, controls) │ └── common/ # Save/load dialog, tutorial overlay │ └── utils/ # Debounce, number formatting 

All game data lives in src/data/*.json. To update after a patch:

1. Edit the JSON files with new/changed tech data
2. Add any new AVIF icons to public/media/tech_icons/
3. Run npm run build

No source code changes needed unless Stellaris adds new inline script types.

The calculator implements the same weight formula as the game:

weight = base_weight × Π(modifier factors) × inline_script_multipliers × (1 + expertise_bonus) × beeline_modifier × (drawn_last ? 0 : 1) 

The 8-step update cascade runs on every empire change:

1. Count researched techs per area/tier
2. Evaluate potential blocks for all techs
3. Update derived atomic facts
4. Check prerequisites (including tier thresholds)
5. Apply conditional tech swaps
6. Compute weights for all available techs
7. Compute delta weights (opportunity cost)
8. Dispatch Monte Carlo simulation to Web Worker

Steps 1–7 run synchronously (~5–15 ms). Step 8 runs asynchronously on a dedicated thread.

If you find this tool useful, consider supporting its development:

MIT — see LICENSE for details.