Oh Oakland, why must you break my heart ... all over again.

It took 12 wrenching innings -- a nearly five-hour battle of attrition -- for the Kansas City Royals to oust the A's with a 9-8 victory in Tuesday's sudden-death wild card face off in Kansas City.

Oakland headed into the eighth inning with a comfortable 7-to-3 lead (thanks in large part to Brandon Moss's two homers), Victory seemed imminent.

But alas ... things fall apart.

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By the end of the ninth, the score was tied at seven, and stayed there that until the A's drove in a single run in the top of the twelfth, three outs away from advancing. And then Kansas City rebounded, and the game ended with Salvador Perez's walk-off single hit weakly down the third-base line, barely escaping Josh Donaldson's glove.

Much like this game, Oakland's odds seemed incredibly promising for the first half of the season: heading into August, the team had the best record in the majors. And then the wilting began

As relief pitcher Sean Doolittle said during an emotional post-game interview: "We got out to a fast start and late in the game we weren't able to hold onto the lead. And it's kind of a microcosm of the year we had."

And just like that, Oakland -- who've made the playoffs the last two years -- are heading home defeated, while Kansas City -- who haven't made the postseason in 29 years -- is off to the face the Anaheim Angels in the best-of-five division series.

Welcome to the drama that is postseason October baseball.

This year, as the NY Times notes, features one of the most intriguing sets of potential geographic face-offs: with a handful of possible World Series matchups involving local rivals: Dodgers-Angels, Nationals-Orioles, Cardinals-Royals and, until the dream died last night, A’s-Giants.

So, if you happened to miss the first six months of the season and are just now tuning into the action (how very convenient!), here's a quick rundown of postseason rules.

Click on each team in the map below for more info

By the numbers

162

Total games each Major League Baseball (MLB) team plays during the 6-month regular season. That's a lot of baseball. Compare that to other professional sports: football teams each play 16 regular season games (albeit with a tad bit more physical contact); basketball and hockey teams each play 82 regular season games.

30

MLB teams. Half in the National League half in the American League. Each league has three divisions - East, Central, West - with five teams in each division.

10

Postseason teams. That includes the six teams with the best records in their divisions plus the wild card teams. This year's division winners, in order of league rank:

National: Washington Nationals; LA Dodgers; St. Louis Cardinals

American: Anaheim Angels; Baltimore Orioles; Detroit Tigers

4

Wild card teams. These are the two leftover clubs from each league who didn't win their divisions but have the next best records. Until a few years ago, only one wild card team from each league made it into the postseason, facing the league's top seed in the best-of-five division series.. In 2012, though, the rules changed.

For the first time in MLB history, a second wild-card team was added to each league with those two teams facing each other in a sudden death, single-elimination contest. The team with the better record gets home field advantage. The winner then advances to the divisional series against the team in the same league with the best record. This year -- despite the A's crushing defeat -- the Bay Area benefited handily from the new rule: both Oakland and San Francisco grabbed the second wild card spots, barely eking their way into the postseason. Tonight (Wednesday) the Giants battle the Pittsburgh Pirates in a wild card death match for a playoff berth.

2

League championship series. Both the American League and National League series is a best-of-seven game contest played by the teams who won their division series. Like before, the team with the best record has home-field advantage.

1

World Series championship! Finally. After a long, hard slog, the American League and National League champions face-off at the end of October in a best-of-seven series. Home-field advantage is determined by the winning league in the All-Star Game. This one's for the whole megillah!

And then finally, Americans can give their full attention to that other strange and slightly more bone-crushing sport we seem so fond of.

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