It's hard to think of a speedrun more pure than Super Mario Bros. There have been myriad "classic" or popular speedruns that have been born out of competition, random luck, or perseverance, like the blindfolded Punch Out!! runs or anything involving Mega Man X, but I always find myself gravitating toward the NES Mario for some reason.
In this case it's actually the SNES remake of Mario Bros. (via the great Mario All-Stars), which actually makes things a little harder. Due to the limitations of the NES enemies could actually despawn if there were too many on-screen, and the hitboxes were a bit smaller. As speedrunner Kosmic points out, several levels (4-2/8-4) are slower because of it.
That didn't stop him from setting a new world record though. On April 6 he achieved the world record time of 5:01.30, beating out the previous time of 5:01.701 from Andrewg1990. Kosmic will be at Summer Games Done Quick if you want to see him live, where he'll be performing a warp-less run and a one-handed run.
via destructoid https://www.destructoid.com/super-mario-bros-speedrun-master-kosmic-sets-another-world-record-497920.phtml