Very good! Takes one simple idea -- a third, time-travelling portal -- and thinks through all the different ways it can work with the established Portal rules and gizmos. Well thought out, very challenging, but not unfair (beyond perhaps one timing-based puzzle). Check it out!

Very good! Takes one simple idea -- a third, time-travelling portal -- and thinks through all the different ways it can work with the established Portal rules and gizmos. Well thought out, very challenging, but not unfair (beyond perhaps one timing-based puzzle). Check it out!