Manchester United booked their place in the FA Cup final after penalty drama and will be back at Wembley in June to take on their noisy neighbours.
The contest couldn't be settled in 90 minutes with both sides enjoying purple patches with the ball, but chances were very much at a premium. The Seagulls enjoyed the better of the play as they eyed a third successive win over United following victories this season and last.
Extra-time followed a familiar pattern with the game becoming increasingly stretched. Marcus Rashford had a deflected effort impressive saved by Robert Sanchez whilst the Seagulls continued to spurn their impressive positions with poor touches and passes.
The game, which had long looked destined for penalties, ended up going that way. An exhibition of spot kicks saw it go to sudden death, with the first ten all scored before Solly March missed the vital spot kick, allowing Victor Lindelof to grab the headline moment.
Here are five talking points from Wembley.
The cup double is on
Hopes of a three-trophy season were ended in midweek when Sevilla tore United apart in Spain, but a promising first season under Erik ten Hag remains on the cards with both domestic cups now within their grasp.
Manchester City stand between the Red Devils and a first FA Cup since 2016, but they've proven they can get the better of their local neighbours and already this term they've tasted success at Wembley, whilst they could also halt City's hopes of winning the treble.
A top four spot is edging closer and that, coupled with two pieces of silverware, would suggest United are very much on the right path, albeit some aspects need ironing out. A Manchester derby final with attract the attention of fans and a red ribbon on the trophy would be an excellent base for which the club can build on.
On the spot
The last time United took part in a semi-final penalty shootout was in 2009 against Everton when the Toffees ended their hopes in the competition. Last term it was Middlesbrough who took advantage of spot kicks to end their hopes - so it is fair to say United and penalties haven't always mixed well.
They were able to buck that trend however as Solly March missed the crucial penalty, which allowed the Manchester outfit to take advantage. United were far from at their vintage best during the 120 minutes but showed they had it in them to handle the pressure moments when the time came.
The Red Devils had lost seven of their last eight shootouts, but will be happy to amend that stat.
No cutting edge still an issue
United's desperation was underlined in midweek when a half-fit Rashford was thrown on against Sevilla as they sought some much needed firepower. The forward has enjoyed the best season of his career, but there is very much an over reliance on him.
Fernandes produces the odd moment, such is his appetite for a long range effort. However, for the quality of the names on the pitch, United should pose much more of a threat in the final third, but that simply isn't the case. Antony, whose price tag continues to weigh heavy, must produce more.
The pattern of the game was largely Brighton applying pressure and United struggling to return serve with their players seemingly unable to pose any serious - and consistent - threat with their best moments largely coming on the counter.
De Gea's limitations remain
Much was made on Thursday night, as it has been all season, of the Spaniard's inability to play with his feet as his manager would like. His passing and decision making cost United twice in the loss at Sevilla, which led to questions over his long-term suitability.
De Gea's contract is winding down in Manchester, leaving the club with a decision to make. The goalkeeper is keen to remain, but displays like the one at Wembley may not help his cause. Whilst Brighton dominated the ball, with their No.1 getting involved in their build-up play, the Red Devils continued to go long.
That was largely down to De Gea's route one tactics with the goalkeeper's first option often being a long punt downfield, with United not having the players to suit that direct style.
Brighton here to stay
It doesn't matter whether they lose managers or key men, they just keep rolling on. Brighton have long been hailed for how they operate as a club, often punching above their weight. This term though they've, by some distance, produced their best season-long performance.
Europe beckons for the Seagulls, who may well see one or two of their prized assets leave this summer, whilst their manager too will attract attention. For huge chunks of their semi-final though they were the better side, dominating possession against United.
They look incredibly comfortable in their own skin with their midseason manager change perhaps making them even better to watch. Whether or not the personnel changes at the Amex remains to be seen, but the decision makers are more than competent and seeing them in the latter stages of competitions like this could well become a regular thing.
