As expected, the key game determining the 2018 Cotsen Open winner was Round 4 on Sunday morning, when defending 
champion Mark Lee 7d faced Andy Liu 1P, both 3-0. The two players wasted no time getting down to business, beginning playing while the room was still bustling with noisy players finding their seats. The opening played out very quickly, with Liu taking cash and 
Lee sketching out a large moyo. Liu’s AlphaGo-like move 45, adjacent to the center star point on the very edge of Lee’s right-side moyo, set the tone for the rest of the game, as Lee fiercely attacked Liu’s eyeless dragon and the fighting got ever more complicated as ladders and nets spiraled out across the board (see game record, below). As more than 130 viewers on KGS hotly debated whether Liu’s group would survive, the players moved into an extended and complex endgame battle for sente and the handful of points that would secure a victory, and the championship. In the end, Lee’s endgame tesujis prevailed and Liu resigned, a few points behind on the board, plus komi. “Andy’s very strong,” Lee said, “it was a tough game.” Liu returned the compliment, saying that Lee “played well; it was really a great game.” Lee went on to win the final round against Luan Bo 6d to complete his 5-0 sweep and collect his fourth consecutive Cotsen Open championship. “We may need to re-name this the Mark Lee title,” joked Eric Cotsen, who thanked all the players for turning out for the 29th annual tournament. “You’re what makes this event so special.”
Results
Open section: 1. Mark Lee 5 wins; 2. Andy Liu 4 wins; 3. Bowen Zhang 4 wins; 4. Yufei Jin 3 wins; 5. Bo Luan 3 wins; 6. Qi-Hao Zhou 3 wins
Division A: 1. Yuelun Yang 5 wins; 2. William He 5 wins; 3. King Bi 4 wins
Division B: 1. Josiah Frias 5 wins; 2. Ernest French 5 wins; 3. Kosuke Sato 4 wins
Division C: 1. Anthony Long 5 wins; 2. Han Chung 5 wins; 3. Michael Mei 4 wins
Division D: 1. Lev Marcus 5 wins; 2. Chris Kaynor 5 wins; 3. Luke Belyeu 4 wins
Division E: 1. Tony Yang 5 wins; 2. Kevin Yang 5 wins; 5. Lucia Moscola 5 wins
Club winner: Orange County Go Club
– report/photos by Chris Garlock; click here for the 2018 Cotsen Open album on Facebook
