:root {
  --nbg-ink: #173f3b;
  --nbg-green: #159a87;
  --nbg-green-dark: #087466;
  --nbg-mint: #e8f8f4;
  --nbg-yellow: #f6c54c;
  --nbg-coral: #f06f67;
  --nbg-border: #cfe6e1;
  --nbg-shadow: 0 16px 42px rgba(25, 88, 78, .13);
}

body.nk-route-game.nbg-body { background: linear-gradient(180deg,#f4fcfa 0,#fff 520px); color: var(--nbg-ink); }
.nbg-body *, .nbg-body *::before, .nbg-body *::after { box-sizing: border-box; }
.nbg-body .math-header a { text-decoration: none; }
.nbg-body .math-nav { display: flex; gap: 8px; }
.nbg-body .math-nav a { padding: 10px 14px; border-radius: 12px; color: var(--nbg-ink); font-weight: 800; }
.nbg-body .math-nav a:hover,.nbg-body .math-nav a.active { color: var(--nbg-green-dark); background: var(--nbg-mint); }
.nbg-shell { min-height: 70vh; padding: 22px 18px 70px; }
.nbg-shell > .back-button { display: inline-flex; margin: 0 0 18px; color: #22635b; font-weight: 800; text-decoration: none; }
#brain-game-root { max-width: 980px; margin: 0 auto; }

.nbg-intro { display: grid; grid-template-columns: 220px minmax(0,1fr); gap: 36px; align-items: start; padding: 38px; border: 1px solid var(--nbg-border); border-radius: 30px; background: rgba(255,255,255,.96); box-shadow: var(--nbg-shadow); }
.nbg-intro-icon { position: sticky; top: 24px; display: grid; place-items: center; aspect-ratio: 1; border-radius: 34% 66% 58% 42% / 45% 40% 60% 55%; color: #fff; background: linear-gradient(145deg,var(--nbg-green),#49bda5); font-size: 5rem; font-weight: 950; box-shadow: inset 0 -12px 0 rgba(0,0,0,.07),0 18px 34px rgba(21,154,135,.22); }
.nbg-intro-copy h1 { margin: 8px 0 14px; font-size: clamp(2rem,5vw,3.15rem); line-height: 1.15; letter-spacing: .02em; }
.nbg-lead { margin: 0; color: #355e59; font-size: 1.08rem; line-height: 1.9; }
.nbg-intro-copy h2 { margin: 28px 0 12px; font-size: 1.15rem; }
.nbg-levels { display: grid; grid-template-columns: repeat(3,1fr); gap: 10px; }
.nbg-levels button { min-height: 88px; padding: 13px 9px; border: 2px solid var(--nbg-border); border-radius: 17px; color: var(--nbg-ink); background: #fff; cursor: pointer; }
.nbg-levels button b,.nbg-levels button span { display: block; }
.nbg-levels button b { font-size: 1.05rem; }
.nbg-levels button span { margin-top: 6px; color: #62807c; font-size: .85rem; }
.nbg-levels button.selected { border-color: var(--nbg-green); background: var(--nbg-mint); box-shadow: 0 0 0 3px rgba(21,154,135,.1); }
.nbg-note { display: grid; grid-template-columns: auto 1fr; gap: 12px; align-items: start; margin: 20px 0; padding: 15px 17px; border-radius: 16px; background: #fff8df; }
.nbg-note b { padding: 4px 9px; border-radius: 99px; color: #6b4a00; background: var(--nbg-yellow); font-size: .8rem; }
.nbg-note p { margin: 0; line-height: 1.7; }
.nbg-start { width: 100%; min-height: 58px; font-size: 1.08rem; }

.nbg-play-head { display: grid; grid-template-columns: 1fr auto 1fr; align-items: center; gap: 12px; margin-bottom: 11px; }
.nbg-play-head a { color: #23655d; font-weight: 800; text-decoration: none; }
.nbg-play-head > span { font-size: 1rem; }
.nbg-play-head > span b { font-size: 1.4rem; }
.nbg-play-head em { justify-self: end; padding: 7px 12px; border-radius: 99px; color: #087466; background: var(--nbg-mint); font-style: normal; font-weight: 850; }
.nbg-progress { height: 10px; margin-bottom: 18px; overflow: hidden; border-radius: 99px; background: #dfeeea; }
.nbg-progress i { display: block; height: 100%; border-radius: inherit; background: linear-gradient(90deg,var(--nbg-green),#63c7aa); transition: width .25s ease; }
.nbg-question-card { min-height: 520px; padding: 34px; border: 1px solid var(--nbg-border); border-radius: 28px; text-align: center; background: #fff; box-shadow: var(--nbg-shadow); }
.nbg-question-card h1 { max-width: 760px; margin: 9px auto 24px; font-size: clamp(1.7rem,4vw,2.55rem); line-height: 1.35; }
.nbg-subprompt { margin: -8px 0 25px; color: #66817e; }
.nbg-main-number,.nbg-memory-value { display: grid; place-items: center; width: min(330px,80vw); min-height: 210px; margin: 20px auto 28px; border: 4px solid #b8e1d8; border-radius: 28px; color: var(--nbg-ink); background: linear-gradient(145deg,#f7fffd,#e4f7f2); font-size: clamp(4.6rem,18vw,8.5rem); font-weight: 950; font-variant-numeric: tabular-nums; box-shadow: inset 0 0 0 9px #fff; }
.nbg-memory-value.compact { min-height: 180px; font-size: 7.5rem; }
.nbg-waiting p { color: #57736f; font-size: 1rem; }
.nbg-choices { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 14px; max-width: 760px; margin: 26px auto 0; }
.nbg-choices button { min-height: 84px; padding: 16px 10px; border: 2px solid color-mix(in srgb,var(--choice) 60%,white); border-radius: 19px; color: var(--nbg-ink); background: color-mix(in srgb,var(--choice) 8%,white); cursor: pointer; transition: transform .12s ease,box-shadow .12s ease; }
.nbg-choices button:hover { transform: translateY(-2px); box-shadow: 0 8px 20px rgba(20,80,70,.12); }
.nbg-choices button span { display: block; font-size: 1.3rem; font-weight: 900; }
.nbg-choices button small { display: block; margin-top: 5px; color: #607a76; }
.nbg-choices button.correct { border-color: #2ca06f; background: #e8f8ee; }
.nbg-choices button.wrong { border-color: #dc615b; background: #fff0ef; }
.nbg-feedback { max-width: 760px; min-height: 52px; margin: 24px auto 0; padding: 14px 18px; border-radius: 15px; color: #466963; background: #f0f8f6; }
.nbg-feedback.result { display: flex; flex-wrap: wrap; justify-content: center; gap: 7px 13px; align-items: center; }
.nbg-feedback.result b { font-size: 1.12rem; }
.nbg-feedback.result span { width: 100%; }
.nbg-feedback.result em { color: #087466; font-style: normal; font-weight: 900; }
.nbg-feedback.ok { color: #12633f; background: #e9f8ee; }
.nbg-feedback.ng { color: #8b3431; background: #fff0ef; }
.nbg-next-actions { margin: 15px auto 0; }
.nbg-next-actions .button { min-width: 230px; }

.nbg-equation { display: flex; justify-content: center; align-items: center; gap: clamp(10px,3vw,28px); margin: 65px auto 30px; font-size: clamp(2.6rem,8vw,5rem); font-weight: 950; }
.nbg-equation strong { display: grid; place-items: center; width: 1.35em; height: 1.35em; border-radius: 18px; color: #fff; background: var(--nbg-coral); }
.nbg-color-board { display: grid; grid-template-columns: repeat(4,1fr); gap: 7px; width: min(390px,86vw); margin: 5px auto 22px; padding: 12px; border-radius: 22px; background: #eff7f5; }
.nbg-color-board.hard { grid-template-columns: repeat(6,1fr); }
.nbg-color-board i { display: block; aspect-ratio: 1; border: 3px solid rgba(255,255,255,.9); border-radius: 10px; box-shadow: 0 2px 5px rgba(0,0,0,.08); }

.nbg-built-word { display: flex; justify-content: center; align-items: center; min-height: 88px; max-width: 680px; margin: 30px auto 22px; padding: 14px; border: 3px dashed #8fcabe; border-radius: 18px; background: #f6fffd; font-size: clamp(2rem,7vw,3.6rem); font-weight: 900; letter-spacing: .12em; }
.nbg-built-word span { color: #7c9994; font-size: 1rem; font-weight: 700; letter-spacing: 0; }
.nbg-letter-pieces { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin: 0 auto 16px; }
.nbg-letter-pieces button { min-width: 62px; min-height: 62px; padding: 8px 14px; border: 2px solid #82c6b8; border-radius: 15px; color: var(--nbg-ink); background: #fff; font-size: 1.7rem; font-weight: 900; cursor: pointer; }
.nbg-letter-pieces button:disabled { opacity: .25; transform: scale(.92); }
.nbg-undo { padding: 9px 16px; border: 1px solid var(--nbg-border); border-radius: 99px; color: #496b66; background: #fff; cursor: pointer; }

.nbg-light-board { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; width: min(430px,86vw); margin: 28px auto; padding: 16px; border-radius: 26px; background: #183f3b; }
.nbg-light-board button { aspect-ratio: 1; border: 3px solid rgba(255,255,255,.2); border-radius: 20px; background: #2b645d; cursor: pointer; transition: transform .12s,background .12s,box-shadow .12s; }
.nbg-light-board button.lit { z-index: 1; transform: scale(1.08); border-color: #fff; background: #ffe46d; box-shadow: 0 0 0 7px rgba(255,228,109,.25),0 0 28px #ffe46d; }
.nbg-light-board button.pressed { transform: scale(.93); background: #70d4bd; }

.nbg-summary { padding: 38px; border: 1px solid var(--nbg-border); border-radius: 28px; background: #fff; box-shadow: var(--nbg-shadow); }
.nbg-summary-stats { display: grid; grid-template-columns: repeat(4,1fr); gap: 12px; margin: 28px 0; }
.nbg-summary-stats > div { padding: 18px 10px; border-radius: 18px; text-align: center; background: #eff9f6; }
.nbg-summary-stats small,.nbg-summary-stats b,.nbg-summary-stats span { display: block; }
.nbg-summary-stats b { margin: 4px 0; color: var(--nbg-green-dark); font-size: 2rem; }
.nbg-summary .summary-actions { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; }

.nbg-more-games { max-width: 1180px; margin: 42px auto 0; padding: 28px; border: 1px solid #cfe6e1; border-radius: 28px; background: linear-gradient(145deg,#effbf8,#fff); }
.nbg-more-games-head { margin-bottom: 20px; }
.nbg-more-games-head .eyebrow { color: var(--nbg-green-dark); }
.nbg-more-games-head h2 { margin: 4px 0 6px; font-size: clamp(1.7rem,4vw,2.5rem); }
.nbg-more-games-head p { margin: 0; color: #55726e; }
.nbg-game-grid { display: grid; grid-template-columns: repeat(4,minmax(0,1fr)); gap: 14px; }
.nbg-game-card { display: flex; flex-direction: column; min-height: 240px; padding: 20px; border: 1px solid #d6e9e5; border-radius: 21px; background: #fff; box-shadow: 0 7px 20px rgba(30,100,88,.08); }
.nbg-game-card .nbg-card-icon { display: grid; place-items: center; width: 54px; height: 54px; margin-bottom: 13px; border-radius: 17px; color: #fff; background: var(--card-color,var(--nbg-green)); font-size: 1.35rem; font-weight: 950; }
.nbg-game-card > span { color: var(--nbg-green-dark); font-size: .82rem; font-weight: 850; }
.nbg-game-card h3 { margin: 6px 0 8px; font-size: 1.12rem; line-height: 1.4; }
.nbg-game-card p { flex: 1; margin: 0 0 15px; color: #58736f; font-size: .92rem; line-height: 1.65; }
.nbg-game-card a { display: block; padding: 10px; border-radius: 11px; color: #fff; text-align: center; text-decoration: none; background: var(--nbg-green); font-weight: 850; }

.nbg-records-addon { max-width: 1180px; margin: 28px auto 0; padding: 26px; border: 1px solid var(--nbg-border); border-radius: 24px; background: #fff; }
.nbg-records-addon h2 { margin: 0 0 6px; }
.nbg-records-addon > p { margin: 0 0 18px; color: #58736f; }
.nbg-record-grid { display: grid; grid-template-columns: repeat(4,minmax(0,1fr)); gap: 10px; }
.nbg-record-card { padding: 15px; border-radius: 15px; background: #eff9f6; }
.nbg-record-card b,.nbg-record-card span,.nbg-record-card small { display: block; }
.nbg-record-card span { margin: 7px 0; color: var(--nbg-green-dark); font-size: 1.25rem; font-weight: 900; }
.nbg-record-card small { color: #637d79; }

@media (max-width: 820px) {
  .nbg-intro { grid-template-columns: 1fr; padding: 26px; }
  .nbg-intro-icon { position: static; width: 130px; margin: 0 auto; font-size: 3.2rem; }
  .nbg-game-grid,.nbg-record-grid { grid-template-columns: repeat(2,minmax(0,1fr)); }
}
@media (max-width: 560px) {
  .nbg-body .math-header { height: 70px; padding-inline: 14px; }
  .nbg-body .math-header .brand-logo { width: auto; max-width: 190px; height: 48px; }
  .nbg-body .math-nav a { padding: 8px 9px; font-size: 12px; }
  .nbg-body .math-nav a:last-child { display: none; }
  .nbg-shell { padding: 14px 10px 48px; }
  .nbg-intro,.nbg-question-card,.nbg-summary { padding: 21px 15px; border-radius: 22px; }
  .nbg-levels { grid-template-columns: 1fr; }
  .nbg-levels button { min-height: 64px; }
  .nbg-play-head { grid-template-columns: 1fr auto; }
  .nbg-play-head em { grid-column: 1 / -1; justify-self: center; }
  .nbg-question-card { min-height: 500px; }
  .nbg-choices { grid-template-columns: 1fr; gap: 9px; }
  .nbg-choices button { min-height: 66px; }
  .nbg-equation { margin-top: 35px; }
  .nbg-summary-stats { grid-template-columns: repeat(2,1fr); }
  .nbg-game-grid,.nbg-record-grid { grid-template-columns: 1fr; }
  .nbg-more-games { padding: 20px 14px; border-radius: 22px; }
}
@media (prefers-reduced-motion: reduce) {
  .nbg-body * { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; }
}