Speedrun is a game mode that can be unlocked after reaching level 1000 in any main file by accessing Challenge Mode. In speedrun, some features are disabled, such as events. Your progress bar always goes at full speed, even when idle. The goal is to get from level 1 to level 9001 as quickly as possible.
In the past, getting to milestones 1000 levels apart gave points that could be redeemed for items such as day skips. These bonuses have since been removed. Instead, completion now grants the Speed Runner medal. This medal is rank 100 and grants +50% HP, Evasion, and Critical Damage with random bonuses, making it the equivalent of a permanent +10 Nerf Accepted! medal.