The first half saw Swindon have most of the play, but unable to break down Brighton's defence, the closest their came in the first half to scoring from from a number of corners.
Brighton's barely managed a shot on goal all game, as they sat back to defend their 1-0 away lead.
On 74 minutes Tommy Mooney hit the bar for Swindon, the third time he had down this in the two play off's games, but the shot then went over.
Sam Parkin put Swindon 1-0 up on the night with a close range shot on 81 minutes, when the ball rolled across the goal line before coming to Parkin who made sure that he scored. This forced teh game into extra time.
Rory Fallon put Swindon 2-0 up on the night 7 minutes into extra time, with a close range shot which looked like it had gone wide at first.
With only one minute of extra time reamaining Brighton scored to make it 2-1 on the night, and 2-2 overall to force the game to penalties with a close range header from Adam Virgo.
The game was similiar to the Leeds cup game earlier in the season in that Swindon should have won, but a last minute goal forced to game to go to penalites.
Swindon's first penalty was taken, and scored by Sam Parkin, their second was taken by Heywood who also scored, the third by Mooney which was saved, the fourth by Fallon which he scored, and Swindon's final penalty was taken from Andy Gurney who hit the post. Brighton's only took 4 penalties, and scored all of them to make it a 4-3 win on penalties.
Overall Brighton, as the ammitted were very luckly to go through after it was Swindon that won on the night, and played the best over the two games, but itr is Brighton who now meet Bristol City in the play off finals in Cardiff next week.