A game-time snapshot. Null means unobserved/uninitialized; never advance on a wall clock.
Readonly
Completed fraction, from 0 to 1; null when unreadable.
Remaining game seconds, or null when unavailable.
Positive total game seconds, or null when unavailable.
A game-time snapshot. Null means unobserved/uninitialized; never advance on a wall clock.