A company which actively develops software has the ability to snapshot a stable development tree and call it a "New Engine"? Shock horror. There does come a po

A company which actively develops software has the ability to snapshot a stable development tree and call it a "New Engine"? Shock horror. There does come a point where the architectural decisions made in the past no longer make any sense & core rewrite is in order. Valve are a quality company & know to avoid the second system effect. At some point you may as well label what you've written as a 'new system' even if you can trace its development path in an evolutionary fashion from the old to the new.