In June 2012, Sophie Houlden entered a contest named "7DFPS" which aims to create first-person-shooters in only 7 days.
During the competition she developed "Splat Death Salad", a multiplayer FPS with some fresh gamemodes (Blackbox, You only live thrice, Blast-ketball,...). Players can also change their appearence by customizing their headmodels and colors. Sophie made a call for additional headmodels on twitter that resulted in a fair amount of headmodels to choose from.
On June 15th, when 7dfps came to an end and over 100 games were created, Sophie released the binaries along with the source to the game. One day later, SDS was released on Kongregate.
2 days later, SDS PEW was born. It started as a bugfix repository on github of the original source and quickly evolved into a patch adding new comfort-features and changing gameplay to be more competitive. After getting requests for even more changes work on version 0.2 started and added loads of features and new gamemodes.
On June 28th, SDS got updated to 1.1 featuring 2 new gamemodes, 3 new weapons and 2 new maps. One day later Sophie released a making-of-article including the source for SDS 1.1.
After playing and liking SDS 1.1 the maps "The Octadrome" and "Conflict Room" got modified for better gameplay and added into SDS PEW 0.3. The gamemodes and weapons didn't make it into the release as they didn't feel right.
Besides to the new maps 0.3 introduced jumppads and major movement-changes.