Physics are part of the physics engine on ROBLOX. The original physics engine was considered a very realistic engine by the staff members, but has been questioned due to the amount of fails and inaccuracies with the engines. In 2013, there was an articulated physics engine being worked on but was stopped because of it being slow and not solving collisions, and in mid 2015, a new collisions system was released first known as experimental physics but is now known as PGS physics. Before PGS physics, ROBLOX used a faster but more inaccurate solver known as spring physics.