Sussex ended day two of their crucial county championship clash with Gloucestershire more than 100 ahead and with three first-innings wickets intact.
David Payne claimed 3-58 to keep promotion-chasing Gloucestershire in contention but Phil Salt top-scored with 64 and Luke Wells made 42 as Sussex, at one stage handily-placed on 151-1, established a first-innings advantage.
Payne inspired a recovery of sorts, but the visitors were on 313-7 by the close of a stop-start day on which 23 overs were lost to bad light despite the County Ground floodlights being turned on throughout.
Sussex boast a useful lead of 113 at the halfway stage, but Gloucestershire can take some encouragement from a pitch which is already flattening out and an improved weather forecast for the next two days.
Salt said: "It was a stop-start day and the weather was frustrating. We're disappointed to have lost 23 overs, but we'd have taken this position had it been offered at the start of the day. Nobody has made a really big score and yet we have a really useful lead. We need to try to build on that in the morning and then apply pressure with the ball.
"It's a difficult pitch to score on, especially when the bowlers bowl straight. You have to be patient and careful with your shot selection. But we've shown that, if you apply yourself for long enough, it is possible to build partnerships. We expect the pitch to flatten out a bit as the game goes on and we fancy ourselves to chase a target on the last day. We are in a better position than all three of the teams immediately above us and this is a big opportunity to put ourselves back in the promotion frame."
The chief difference between the sides so far being the erratic contribution of new Gloucestershire overseas signing Shannon Gabriel, who no-balled on 10 occasions and conceded 94 runs from 16 overs.
Resuming on 73 without loss, Sussex picked up where they left off at the end of the first day, Wells and Salt scoring at a good tempo on an increasingly low and slow pitch. Their opening stand was worth 100 in the 25th over when the home side finally engineered the breakthrough they so desperately needed.
Gloucestershire's most effective bowler, Payne slanted a teasing delivery across Salt, who edged to second slip and was well held by James Bracey for 64. His 83-ball innings featured 11 fours and afforded the reply solid foundations.
Thereafter, Wells came out of his shell and took charge of a progressive stand of 51 for the second wicket with Tom Haines as Sussex threatened to take complete control of the game.
Called into the attack shortly before lunch, slow left-armer Tom Smith provided overdue relief for the home side, luring Haines into front-foot indiscretion and inducing him to snick to Bracey at second slip for 22. Encouraged by that success, Gloucestershire's bowlers built pressure to initiate a slide in which Sussex subsided from 151-1 to 177-4 during an afternoon session in which nine overs were lost to bad light.
Payne inspired the fightback, claiming two wickets for two runs in a six-over burst which contained four maidens. Wells departed soon after lunch for 42, pushing half forward at a length ball and edging to second slip where Bracey again demonstrated safe hands.
Attempting a wholly inappropriate shot in the circumstances, Delray Rawlins was next to go, top-edging a catch to wicketkeeper Gareth Roderick and departing for 10. The fifth wicket pair of Stiaan van Zyl and Ben Brown sought to consolidate, surviving a testing examination at the hands of West Indies paceman Gabriel, who produced his best spell of the match in the late-afternoon gloom.
Obdurate in their resistance, Brown and van Zyl carried Sussex into the lead before the latter was pinned lbw in his crease by Matt Taylor for 28. Following a further break for bad light, Ben Charlesworth took centre stage,the teenage all-rounder claiming two wickets in five balls, removing Brown for 24 and then producing a fine delivery to have Chris Jordan caught behind for six.
Thereafter, David Wiese (40 not out) and Will Beer (28 not out) staged an unbroken partnership of 46 for the eighth wicket, in the process negotiating nine overs against the new ball as Sussex finished ascendant.