  We propose a unifying additive theory for standard conventions in
Combinatorial Game Theory, including normal-, mis\`ere- and scoring-play,
studied by Berlekamp, Conway, Dorbec, Ettinger, Guy, Larsson, Milley, Neto,
Nowakowski, Renault, Santos, Siegel, Sopena, Stewart (1976-2019), and others. A
game {\em universe} is a set of games that satisfies some standard closure
properties. Here, we reveal when the fundamental game comparison problem, ``Is
$G\su H$?'', simplifies to a constructive `local' solution, which generalizes
Conway's foundational result in ONAG (1976) for normal-play games. This happens
in a broad and general fashion whenever a given game universe is {\em
absolute}. Games in an absolute universe satisfy two properties, dubbed {\em
parentality} and {\em saturation}, and we prove that the latter is implied by
the former. Parentality means that any pair of non-empty finite sets of games
is admissible as options, and saturation means that, given any game, the first
player can be favored in a disjunctive sum. Game comparison is at the core of
combinatorial game theory, and for example efficiency of potential reduction
theorems rely on a local comparison. We distinguish between three levels of
game comparison; superordinate (global), basic (semi-constructive) and
subordinate (local) comparison. In proofs, a sometimes tedious challenge faces
a researcher in CGT: in order to disprove an inequality, an explicit
distinguishing game might be required. Here, we explain how this job becomes
obsolete whenever a universe is absolute. Namely, it suffices to see if a pair
of games satisfies a certain Proviso together with a Maintenance of an
inequality.
