GTO (game-theory optimal) play means playing a Nash equilibrium: a strategy no opponent can improve against by deviating, however they adjust. Equivalently, your strategy is unexploitable. That's not the strategy that wins the most against a weak opponent — it's the one that never loses to any counter-strategy, ever.

Take rock-paper-scissors. Play each move exactly ⅓ of the time and every response earns 0 EV against you: nothing beats a true ⅓/⅓/⅓ mix long-term. Skew even slightly — say 40% Rock — and an opponent who notices leans on Paper and prints forever. Poker's multi-street, imperfect-information tree is a vast version of the same idea: an equilibrium caps the best response anyone can find.

Real solvers (PioSOLVER, GTO+) never solve full No-Limit Hold'em exactly — it has far too many information sets. They run iterative algorithms (usually counterfactual regret minimization) that converge toward equilibrium and stop once the leftover exploitability is negligible. "Solved" poker really means "solved to within some small, quantified error."

This app is upfront about how far each number sits from that ideal. Every grade carries a provenance label — Nash-anchored on the short-stack push/fold charts, GTO chart (hand-built) on every other preflop chart, a heuristic-estimate label on postflop numbers — with a tap-able ? that explains it. The full trust ladder, the verdict bands, and the postflop model's constants live on the How this app grades you page; the labels are the short version: a strong guideline, not gospel.