What this is

O27 Baseball is a fictional sport — and a full simulation of it. It's baseball with one structural change: each side bats until it records 27 outs — a single inning instead of nine. Everything else falls out of that move.

A few expectations so you read it right:

• It's not a game you play. There's no manager mode. You simulate seasons and read what happens.
• It's a data-exploration tool. Every page exists to surface stats, standings, and box scores for a human — or an LLM — to interpret.
• Numbers run hot on purpose. ~30+ runs a game, batting averages that can top 1.000. That's the sport, not a bug — see below.

The sport in 90 seconds

1. 27 outs, one inning. One long arc per side instead of nine. A starter keeps going until he's pulled, and his fatigue builds the whole way.
2. Second-chance ABs (the “stay”). On contact, a batter can run (normal baseball) or stay at the plate — runners advance, he keeps hitting, and the contact costs a strike. This is how runs are driven in, and why a hitter can record multiple hits in one at-bat.
3. Jokers. Three tactical pinch-batters a manager can drop into any lineup spot, once per joker per time through the order.
4. The Walk-Back. A home run sends the hitter to third base as a live bonus runner until he's driven in or put out.
5. Declared Seconds. A manager can end his regulation half early and bank the unused outs for a second trip through the lineup later.
6. Variance is the design. There is no “correct” run total to tune toward. If a number looks high, that's usually the sport.

Reading a box score & a stat line

Pitching is measured in outs, not innings — there aren't any. The unfamiliar columns are deliberate:

Confused by a column anywhere in the app? The Glossary defines every abbreviation.

Where to click

The top menu groups everything. Here's what each group is for — links open the real pages.

Games — your home base. Scores · 📰 Gazette (a voiced, news-style writeup of a day's games) · Standings · Schedule · Playoffs. Click any game for its box score, play-by-play, and a Markdown export built for pasting into an LLM.

Players — the people. Players · Teams (rosters & the pitching crew) · Compare · Free Agents.

Stats — the deep end. Leaders · Stat Browser (Fangraphs-style almanac with downloadable bundles) · Analytics · Distributions · Glossary.

League — everything around the games. Transactions · Auction · Economy · Financials · Youth & College (the talent pipeline) · Hall of Fame.

Manage — the control room. Saves (multiple leagues coexist) · Engine Settings (reshape the sport). The Sim button up top advances the calendar (Today / Week / Month / Season).

Make it your own

Engine Settings lets you change the constants the engine reads live — contact, fatigue, parks, weather — and the change takes effect on the next sim. Don't know the knobs? Paste the LLM tuning guide into any capable model with a plain-English wish (“a deadball pitcher's duel”, “a home-run circus”) and it hands back a tuning blob you drop straight into the dashboard.

Go deeper

• Full user guide — the long version of this page.
• The complete rules.
• Every stat, with formulas.
• How the project got here — the arc & changelog.
• Why not just play five innings?

First time? Try this

1. Open Scores and click a final.
2. Read the box score — note pitching is in outs.
3. Hit Standings, then a Leaders board.
4. Open the Glossary for anything odd.
5. Skim the Gazette for the story.