In chess, even a measly draw can be a brow-sweating, teeth-clenching, mind-melting epic.

On Monday, a gorgeous autumn day in New York City, Norway’s Magnus Carlsen, the world champion and No. 1 rated player, sat down in a soundproof room in lower Manhattan to continue his title defense against challenger Sergey Karjakin of Russia, the world No. 9. In their best-of-12 match, the two had fought thus far to two forgettable draws and a 1-1 overall score. A crowd of hundreds assembled in lower Manhattan, and thousands more watched a live stream online, hoping some blood would finally be drawn. It wasn’t. But the crowd did witness a 78-move, bloodless classic.

It’s a tired mathematical chestnut that there are more possible games of chess than there are atoms in the universe. But Monday’s game proved yet again just how many untrod strategic paths are still open to even the most seasoned players, who have played and studied thousands upon thousands of games, week after month after year after decade.

Monday’s game began innocuously — even disappointingly — enough. Carlsen, handling the white pieces, made the first move, sliding his king’s pawn forward two spaces. Karjakin followed suit, knights then entered the fray, and a couple of moves later, they were playing the Berlin Defence of the Ruy Lopez opening, also called the Berlin Wall, in which black trots his two knights into the center, in front of his pawn infantry. The variation has a reputation for being familiar, boring and draw-ish. Chess Twitter quickly became displeased and sarcastic.

Just what we have all been waiting for! A Berlin – wowee!! #CarlsenKarjakin — Nigel Short (@nigelshortchess) November 14, 2016

But things went weird on Move 10 when Carlsen (white) contemplated his next move on this board:

In the standard approach, white would get its rook back to safety on e1. But Carlsen threw a changeup, stopping his rook one square short, on e2. Only three times before had this specific sequence of moves ever been played, per ChessBase. (Moving the rook to e1 had been played over 400 times.) Monday’s game, which had seen familiar moves flying onto the board fast and furious (at least by chess standards), came to a grinding halt. The move was a psychological ploy to throw Karjakin off of his famously well-prepared game, Judit Polgar, a grandmaster, explained during the event’s live stream. And it worked. Karjakin, playing black, reeled. He took over 25 minutes to make his next move, eventually pushing his pawn to b6.

And just one move later — after a little more maneuvering of rooks — the two found themselves playing a sequence of chess moves that no one had ever played before. They found yet another untouched atom in the universe.

Despite being in alien territory, the two played sharp, equal chess for 20 more moves. The computer chess engines gave no real edge to either player, seeing the game as inevitably deadlocked — another dull draw.

And then came Move 30. Karjakin’s (black’s) turn to move:

The computer chess engine Stockfish suggested moving the bishop to h6, getting that piece into the action, and keeping the game level. But Karjakin, perhaps a bit restless, and certainly running short on time for much of the game, opted to attack deep in enemy territory, sliding his rook down to a2. Grandmasters in the spectator gallery whipped out their laptops, sensing something amiss. Everything had changed. Immediately, the dials on the computer engine twitched toward Carlsen, and chess Twitter changed its tune as well.

#CarlsenKarjakin seems too early in the match for Karjakin to lose his patience… (30…Ra2, 31…c5) — Alex Colovic (@GMAlexColovic) November 14, 2016

Looks like Carlsen will take this one! #CarlsenKarjakin #Nrksjakk — Magnus Pynten (@magnuspynt1) November 14, 2016

“Karjakin was seeking activity,” Robert Hess, a grandmaster who’s a contributor at chess.com, told me as we stood staring at the game on one of the venue’s monitors. “He brought his rook down in the hopes of tying the piece down to some of the pawns. But I think he misjudged that what ended up happening is the white knight ended up defending everything beautifully.” While it appeared the rook would menace two lowly pawns, white could simply move one of them to b3, leaving the knight to defend the other pawn, rendering the attack toothless.

For another 40 or so moves, it was Carlsen’s game to lose. And for hours, as he held on to a slight but seemingly decisive advantage, it looked like he’d hold on to win. Karjakin defended valiantly, keeping himself in the game, whittling the pieces down to a manageable but intricate endgame.

Nevertheless, after move 71, Carlsen held a sizeable advantage. Here’s what Carlsen was looking at when it was his turn to move:

The correct play, according to Stockfish, was rook to f7, putting black in check. But Carlsen opted for rook to b7, threatening the black pawn, but allowing black to apply his own threat to white’s knight with rook to a1. That one small slip brought Carlsen’s advantage down like a house of cards after more than six hours of constant play. His position disintegrated, and Karjakin pulled even.

At around 8:40 p.m. Eastern, after nearly seven hours of play and 78 moves each, the two combatants shook hands and agreed to a draw.

“Karjakin has shown that he may bend but he hasn’t broken,” Hess said. Karjakin will move first with the slightly advantageous white pieces on Tuesday, with the competition’s score tied 1.5-1.5 in a race to 6.5.

The game was imperfect but memorable — a noble achievement for a contest between fallible humans. It seems unfair to ask whether the result was due to Karjakin’s expert defense or Carlsen’s snatching a draw from the jaws of victory. The better question: Who wins when an unstoppable force meets an immovable object? Carlsen is known as a grinder — a player who will doggedly pursue any tiny advantage, undeterred by how long it might take or what complications might be involved, to eke out a win. Karjakin, on the other hand, is known as a tenacious and precise defender.

On Monday, neither won. The question has yet to be answered, but there are many games to come. Game 4 begins Tuesday afternoon. I’ll be covering the rest of the games here and on Twitter.