Neil Robertson opened up a 9-7 lead over Mark Allen in an absorbing second-round contest at the World Snooker Championship.
Robertson and Allen could not be separated in the opening session and that theme continued in the evening as the lead changed hands three times.
The opening frame of the evening was a scrappy affair with 30 minutes passing without a pot at one stage but once Robertson got amongst the balls he claimed it with a 72.
He clearly had another century on his mind as he attempted to pot the green with deep screw but only succeeded in chipping the cue ball into the pocket.
Allen hit back straight away with a run of 71 before another scrappy affair followed with Robertson prevailing but again he could not pull away and a break of 77 from Allen saw them go into the mid-session interval level.
The Antrim man then edged ahead with a break of 84 but Robertson racked up century number 99 of the season in the next with a stunning clearance of 137.
The world number one then claimed the final two frames of the night and for the first time in the match, the men were separated by more than one frame.
Marco Fu and Shaun Murphy also came into their evening session tied at 4-4 but Murphy threatened to run away with it as he got off to a flying start.
The 31-year-old took the first three frames of the session without requiring a break higher than 67 but when he registered a 102 clearance to make it 8-4 he looked to be in total control.
Fu is made of stern stuff, though, and he came out after the break and stopped the rot by winning the 13th and 14th frames.
Murphy re-opened his three-frame cushion by taking the next but Fu then registered a break of 136 and will go into Monday evening just 9-7 behind.
Earlier in the day, Judd Trump remained on course for the quarter-finals after splitting the second session with Ryan Day to defend his four-frame lead.
Trailing 6-2 overnight, Day took three of the first four frames thanks to breaks of 107, 80 and 55, but Trump won the next two to keep himself 9-5 to the good.
The Bristolian extended his lead in the next with a break of 64 after Day had made 61, but jawed a frame-ball pink, a failing which had haunted him in Saturday’s first session.
Day pulled it back to 10-6 with a 73 in the final frame, but he faces an uphill battle in Monday evening’s concluding session, needing to win seven out of nine frames.
Dominic Dale is almost assured of his place in the next round after moving within a frame of victory against giant-killer Michael Wasley.
The Welshman had dominated the first session against Ding Junhui’s first-round conqueror and took the opener on Sunday to move 8-1 ahead.
Wasley celebrated light-heartedly after a 66 break in the next and headed out of the arena, but Dale did not concede and forced him to pot the pink and black.
Dale took the next two, the first with a 78 and the second by clearing the colours, and an 89 to take him 11-3 up raised the possibility of the match finishing inside two sessions.
The confident Wasley avoided that fate in style with a 108 to the pink, but Dale took the last to move 12-4 ahead.