BlipIt Baseball Legends

What it is

Watch a nine-inning game play out pitch by pitch with a spoken announcer, or turn on Manager Mode and make the calls: steal, bunt, intentional walk, pinch hitter, defensive shift.

Origin

I started this in 2020, during the pandemic, building it with my then five-year-old son.

The first version went live at blipit.net that June. That month I gave a lightning talk at NextDor on refactoring the game’s code.

Play video: Make Refactoring Fun

2020 to now

Timeline

1. Jun 2020self-playing-baseballShipped

   The first version: a self-playing game with a talking announcer.

2. Feb 2026Revived as BallgameShipped

   Rebuilt as an installable web app, with custom teams.

3. Mar 2026BlipIt Baseball LegendsShipped

   Realism tuning against real baseball, then the rename.

4. May 2026League ModeShipped

   Seasons with a schedule and standings.

Managing, teams and leagues

Auto-play

Games always play themselves: pause, resume, and four speeds from Slow to Instant.

Manager Mode

Decision prompts with a 10-second auto-skip, so the game never stalls waiting for you.

Seeded games

The same seed replays the same game, pitch for pitch.

Custom teams

A team builder with JSON import and export; a checksum on every file catches corrupted imports.

League Mode

An 8-team season of 14 games per team (56 in all), with a round-robin schedule and standings.

Saves, custom teams and career statistics live in the browser’s IndexedDB through RxDB, so everything stays on the player’s device, and a saved game resumes mid-inning with its random generator state intact.

Calibrated against real baseball

In March 2026, simulated games scored and walked far more than real baseball, so the tuning treated realism as a measurement problem.

Before and after

About 14 measured tuning rounds in March 2026, on simulated games run in the browser. Every round followed the same rules: commit a baseline first, run 200 games, change one lever at a time, and let the browser run decide. Targets are approximate Major League averages; no single season is cited. The walk rate never reached its target, and the project’s docs call the remaining gap structural. The final check ran 200 games rather than the 300 originally planned.

Stack and quality

Built with React 19, TypeScript, Vite, RxDB / IndexedDB, Web Speech API, Playwright.

• ✓Determinism testA dedicated Playwright project guards seeded replays
• ✓Coverage floors85% of lines and statements, 90% of functions, 80% of branches
• ✓Baseball reviewA baseball-manager review persona checks gameplay changes

How it was rebuilt

I wrote the 2020 version without AI. Most of the 2026 revival came through pull requests from the GitHub Copilot coding agent, which I merged after review: 119 of the 131 merged pull requests came from Copilot branches, under the same workflow as Verticopolis.

Status

Playable at blipit.net (version 1.0.1). In League Mode, the app marks a larger Standard league and a Full-length season as coming soon.

Last updated Oct 14, 2026.

Contribute

I’m looking for contributors to BlipIt Baseball Legends. The code is open source, and the contributor guide covers setup, the quality gates and how changes get reviewed.

• Contributor guide
• Open issues

Receipts

The public work behind this page.

• The measurement rules for realism tuningIssue #149
• Eleven tuning passesPR #140
• Pitch-count fatiguePR #142
• The final tuning roundPR #150
• Seeded-game determinism testTest
• League ModePR #255
• The rename to BlipIt Baseball LegendsPR #166