:root{--paper:#192126;--panel:#202a30;--key:#2a363e;--ink:#f5f6f3;--muted:#b1bdc3;--line:#3c4b54;--mint:#82f5bb;--mint-hover:#a1facd;--coral:#ff9381;--display:'Space Grotesk',Arial,sans-serif;--body:'DM Sans',Arial,sans-serif;color-scheme:dark}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);font:16px/1.5 var(--body);color:var(--ink)}h1,h2,h3,p{margin:0}button,input,select{font:inherit}button,select,summary{cursor:pointer}button{color:inherit;touch-action:manipulation}button:disabled{cursor:default;opacity:.48}a{color:inherit}button,a,input,select,summary{-webkit-tap-highlight-color:transparent}button:focus-visible,a:focus-visible,summary:focus-visible,select:focus-visible{outline:3px solid var(--mint);outline-offset:4px}input:focus{outline:2px solid var(--mint);outline-offset:3px}[hidden]{display:none!important}.shell{width:min(1100px,calc(100% - 72px));margin-inline:auto}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}.skip-link{position:fixed;top:10px;left:10px;z-index:20;background:var(--mint);color:var(--paper);padding:12px;transform:translateY(-200%)}.skip-link:focus{transform:none}
.site-header{display:flex;justify-content:space-between;align-items:center;gap:20px;min-height:126px;margin-bottom:25px;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:23px;text-decoration:none}.brand-symbols{display:grid;grid-template-columns:repeat(2,27px);gap:2px 6px;font:700 36px/1 var(--display);padding-right:23px;border-right:1px solid #829097}.brand-symbols span:first-child{color:var(--coral)}.brand-symbols span:nth-child(3){color:var(--mint)}.brand-name{font:600 clamp(34px,4.2vw,53px)/1 var(--display);letter-spacing:1px}.header-actions{display:flex;align-items:center;gap:24px}.publisher-link{font-size:14px;color:var(--muted);text-decoration:none;padding:12px 0}.publisher-link:hover{color:var(--mint)}.player-button{display:flex;align-items:center;gap:10px;border:1px solid var(--line);background:var(--panel);border-radius:28px;padding:8px 15px 8px 8px;min-height:48px;font-weight:600;font-size:16px;max-width:225px}.player-button>span:last-child{overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.avatar{display:grid;place-items:center;flex-shrink:0;width:31px;height:31px;border-radius:50%;background:var(--mint);color:var(--paper);font:600 15px var(--display)}.panel{background:var(--panel);border:1px solid var(--line);border-radius:18px}
.choices{padding:24px 27px;margin-bottom:24px}.choice-label{display:flex;justify-content:space-between;align-items:baseline;gap:15px}.choices h2{font-size:13px;line-height:1.3;text-transform:uppercase;letter-spacing:2.4px;font-weight:500}.selection-note{font-size:12px;color:var(--muted)}.operations{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:12px;margin-top:14px}.operation{display:flex;align-items:center;justify-content:center;gap:10px;min-height:62px;border:1px solid #50616d;border-radius:11px;background:var(--key);font:600 17px var(--display);transition:background .15s}.operation .symbol{font:500 32px/1 var(--display)}.operation:hover:not(:disabled),.level:hover:not(:disabled){background:#34464d}.operation[aria-pressed='true'],.level[aria-pressed='true']{background:var(--mint);color:#142a20;border-color:var(--mint)}.operation[aria-pressed='true']:hover:not(:disabled),.level[aria-pressed='true']:hover:not(:disabled){background:var(--mint-hover)}.level-heading{display:flex;align-items:baseline;justify-content:space-between;gap:12px;margin:21px 0 12px}.level-heading p{font-size:12px;color:var(--muted)}.levels{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.level{border:1px solid #50616d;border-radius:10px;background:var(--key);min-height:60px;padding:8px 12px;text-align:center}.level-digits{font:600 22px/1.2 var(--display);letter-spacing:1px}.level-example{font-size:12px;display:block;margin-top:4px;opacity:.8}
.workspace{display:grid;grid-template-columns:minmax(0,1.65fr) minmax(280px,1fr);gap:24px;align-items:start}.play{padding:25px 28px;scroll-margin-top:12px}.play-heading{display:flex;justify-content:space-between;align-items:baseline;gap:12px;margin-bottom:20px}.play-heading h2{font-size:13px;letter-spacing:2px;text-transform:uppercase;font-weight:500}.eyebrow{font-size:12px;letter-spacing:.5px;color:var(--muted)}.play-heading .eyebrow{font-size:12px}.scoreboard{display:grid;grid-template-columns:1fr 1fr;border:1px solid var(--line);border-radius:13px;padding:15px 0;text-align:center;background:#1c252b}.scoreboard>div+div{border-left:1px solid var(--line)}.scoreboard span{display:block;font-size:12px;letter-spacing:2px;margin-bottom:3px;color:var(--muted)}.scoreboard strong{font:500 46px/1.2 var(--display);font-variant-numeric:tabular-nums;letter-spacing:1px}.scoreboard .timer{color:var(--mint)}.scoreboard .timer.urgent{color:var(--coral)}.time-track{height:3px;background:#334249;margin:16px 2px 0;border-radius:2px;overflow:hidden}.time-track>span{display:block;width:100%;height:100%;background:var(--mint)}.setup{text-align:center;padding:26px 0 2px}.example-equation{font:500 48px/1.2 var(--display);letter-spacing:1px;color:#9dadae;margin-bottom:20px}.setup h3{font:500 21px/1.35 var(--display);margin-bottom:8px}.setup>p:not(.example-equation){color:var(--muted);font-size:16px}.setup .primary-button{width:100%;margin-top:24px}.setup .input-hint{font-size:12px!important;margin-top:15px}.primary-button{border:1px solid var(--mint);border-radius:11px;background:var(--mint);color:#132a20;min-height:54px;padding:13px 22px;font-weight:700;display:inline-flex;justify-content:center;align-items:center}.primary-button:hover{background:var(--mint-hover)}.secondary-button{border:1px solid #60717d;border-radius:11px;background:var(--key);min-height:54px;padding:13px 18px;font-weight:500}.secondary-button:hover{background:#34464d}.game{max-width:410px;margin:auto}.equation{font:500 clamp(38px,5.7vw,62px)/1.2 var(--display);letter-spacing:1px;text-align:center;padding:22px 0 17px;white-space:nowrap}.equation .operator{padding:0 10px}#answer{width:100%;height:64px;border:1px solid #899da9;border-radius:11px;text-align:center;background:#192228;color:var(--ink);font:500 37px/1 var(--display);caret-color:var(--mint)}#answer::placeholder{color:#93a0a7}#answer:focus{outline:2px solid #82f5ba60;outline-offset:2px;border-color:var(--mint)}#answer[aria-invalid='true']{border-color:var(--coral)}.feedback{min-height:31px;text-align:center;font-size:14px;line-height:1.4;padding:6px 0;color:var(--muted)}.feedback.correct{color:var(--mint)}.feedback.incorrect{color:var(--coral)}.keypad{display:grid;grid-template-columns:repeat(3,1fr);gap:9px}.keypad button{min-height:57px;border:1px solid #42525e;border-bottom-width:3px;border-radius:9px;background:var(--key);font:500 27px var(--display)}.keypad button:hover{background:#354751}.keypad button:active{background:#435a63;border-bottom-width:1px}.keypad .utility-key{font:400 16px var(--body);color:var(--muted)}.keypad .submit-key{grid-column:1/-1;display:flex;justify-content:space-between;align-items:center;background:var(--mint);border-color:var(--mint);color:#142a20;font:700 17px var(--body);padding:0 18px;margin-top:5px}.keypad .submit-key:hover{background:var(--mint-hover)}.submit-key>span{font-size:12px;font-weight:400}.game-bottom{display:flex;justify-content:space-between;align-items:center;gap:12px;border-top:1px solid var(--line);margin-top:17px;padding-top:3px}.game-bottom p{font-size:12px;color:var(--muted)}.text-button{border:0;background:transparent;color:var(--muted);font-size:14px;min-height:44px;padding:8px 0;text-decoration:underline;text-underline-offset:3px}.text-button:hover{color:var(--ink)}
.leaderboard{padding:24px}.leaderboard-heading{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-bottom:18px}.leaderboard h2{font:600 28px/1.25 var(--display);letter-spacing:-.5px}.demo-pill{font-size:12px;font-weight:500;letter-spacing:1px;border:1px solid #60746e;color:var(--mint);padding:3px 7px;border-radius:5px}select{width:100%;min-height:44px;border:1px solid #50616d;border-radius:8px;padding:8px 11px;background:#1b252b;color:var(--ink);font-size:14px}select+label+select{margin-top:8px}.leaderboard-caption{color:var(--muted);font-size:14px;line-height:1.6;margin:15px 0 25px}.ranking-head{display:flex;justify-content:space-between;color:var(--muted);font-size:12px;letter-spacing:1.5px;padding:0 5px 10px}.rankings{list-style:none;padding:0;margin:0}.rankings li{display:grid;grid-template-columns:22px minmax(0,1fr) auto;gap:10px;align-items:center;padding:15px 10px;border:1px solid var(--line);border-radius:10px;margin-bottom:10px}.rank-number{font:500 19px var(--display);color:var(--muted)}.rank-name{font-size:15px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.rank-score{text-align:right;font:600 25px/1.2 var(--display)}.rank-score small{display:block;font:400 12px/1.5 var(--body);color:var(--muted);margin-top:3px}.rankings .is-you{border-color:#5f9f81;background:#243b32}.is-you .rank-name{color:var(--mint)}.is-you .rank-number{color:var(--coral)}.your-best{margin-top:24px;border-top:1px solid #64747d;padding-top:19px;display:grid;gap:5px}.your-best>span{font-size:13px;color:var(--muted)}.your-best strong{font:500 18px/1.5 var(--display)}.preview-note{font-size:12px;color:var(--muted);margin-top:17px;line-height:1.7}
.results{padding:7px 0}.results h2{font:500 37px/1.2 var(--display);margin:8px 0 12px}.muted{color:var(--muted);font-size:16px}.result-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:9px;margin:23px 0}.result-stats>div{background:#19242a;border:1px solid var(--line);border-radius:10px;padding:18px 7px;text-align:center}.result-stats strong{font:500 34px/1.25 var(--display);display:block}.result-stats span{display:block;font-size:12px;letter-spacing:.8px;color:var(--muted);margin-top:5px}.personal-best{color:var(--mint);font-size:15px;font-weight:600;margin:0 0 10px}.result-actions{display:flex;gap:12px;flex-wrap:wrap;margin:24px 0}details{border-top:1px solid var(--line);padding-top:13px}summary{min-height:44px;padding:8px 0;font-size:16px}#review-list{list-style:none;padding:0;margin:0}#review-list li{display:grid;grid-template-columns:25px 1fr;gap:10px;border-top:1px solid var(--line);padding:15px 0}.review-number{color:var(--muted);font-size:14px}#review-list strong{font:500 20px var(--display)}#review-list p{font-size:14px;color:var(--muted);margin-top:3px}.review-correct{color:var(--mint)}.review-wrong{color:var(--coral)}.storage-note{padding:15px;background:#402f27;color:#ffe7b1;border-radius:8px;font-size:14px;margin:18px 0}
footer{display:flex;align-items:center;justify-content:space-between;gap:20px;border-top:1px solid var(--line);margin-top:30px!important;padding:23px 0;color:var(--muted);font-size:14px}footer>span:first-child{color:var(--ink);font:600 20px var(--display)}footer>a{color:var(--muted);text-decoration:none}footer>a:hover{color:var(--mint)}.preview-pill{font-size:12px;letter-spacing:1px}dialog{padding:30px;border:1px solid #53656f;border-radius:18px;background:var(--panel);color:var(--ink);width:min(440px,calc(100% - 32px));max-height:calc(100dvh - 32px);overflow:auto;box-shadow:0 20px 100px #0005}dialog::backdrop{background:#10171dcc;backdrop-filter:blur(4px)}.dialog-symbols{font:500 30px var(--display);color:var(--mint);display:block;margin-bottom:22px}dialog h2{font:500 31px/1.15 var(--display);margin:0 0 16px}.dialog-description{font-size:16px;color:var(--muted);margin:0 0 20px}#profile-form>label:not(.remember-label){display:block;font-size:14px;margin-bottom:7px}#nickname{width:100%;min-height:49px;border:1px solid #6c7e89;border-radius:9px;background:#172128;padding:10px 12px;color:var(--ink);font-size:16px}.field-help{color:var(--muted);font-size:12px;margin-top:8px}.remember-label{display:flex;align-items:center;gap:10px;font-size:14px;color:var(--ink);margin:19px 0 6px}.remember-label input{accent-color:var(--mint);width:18px;height:18px}#profile-form>.primary-button{width:100%;margin-top:20px}.profile-cancel{display:block;margin:7px auto 0}.quit-actions{display:grid;gap:10px}.noscript{position:fixed;inset:30% 15%;background:var(--panel);padding:30px;box-shadow:0 0 0 100vmax #0008}
@media(max-width:1050px){.shell{width:calc(100% - 48px)}.publisher-link{display:none}.workspace{grid-template-columns:minmax(0,1.6fr) minmax(270px,1fr);gap:18px}.play{padding:22px}.play-heading{display:block}.play-heading .eyebrow{display:block;margin-top:6px}.operation{font-size:16px;gap:7px}.operation .symbol{font-size:27px}.leaderboard{padding:21px}.leaderboard h2{font-size:25px}}
@media(max-width:740px){.workspace{grid-template-columns:minmax(0,1fr)}.site-header{min-height:105px;margin-bottom:20px}.brand-name{font-size:40px}.operations{grid-template-columns:repeat(2,minmax(0,1fr))}.operation{font-size:17px;min-height:54px}.choices{padding:20px}.choice-label{display:block}.selection-note{display:block;margin-top:8px}.level-heading{align-items:flex-start}.level-heading p{max-width:180px;text-align:right}.play-heading{display:flex}.play-heading .eyebrow{margin-top:0}.leaderboard{margin-top:0}.leaderboard select{width:calc(50% - 6px)}select+label+select{margin:0 0 0 8px}.rankings li{grid-template-columns:25px minmax(0,1fr) auto}.game{max-width:430px}.setup{max-width:430px;margin:auto}}
@media(max-width:480px){.shell{width:calc(100% - 28px)}.site-header{gap:12px;min-height:92px;margin-bottom:16px}.brand{gap:12px}.brand-name{font-size:30px;letter-spacing:0}.brand-symbols{grid-template-columns:repeat(2,17px);gap:2px 3px;font-size:24px;padding-right:12px}.player-button{font-size:14px;max-width:135px;min-height:44px;padding:6px 10px 6px 6px;gap:7px}.avatar{width:27px;height:27px;font-size:13px}.choices{padding:18px 15px;margin-bottom:16px}.choices h2{font-size:12px;letter-spacing:1.7px}.operations{gap:9px;margin-top:12px}.operation{min-height:53px;font-size:15px;gap:8px}.level-heading{margin-top:18px;gap:10px}.level-heading p{font-size:12px;line-height:1.3}.levels{gap:8px}.level{padding:8px 5px;min-height:61px}.level-digits{font-size:21px;letter-spacing:0}.level-example{font-size:12px}.play{padding:20px 16px}.play-heading{display:block;margin-bottom:15px}.play-heading h2{font-size:12px}.play-heading .eyebrow{margin-top:6px}.scoreboard{padding:12px 0}.scoreboard strong{font-size:39px}.scoreboard span{font-size:12px;letter-spacing:1.5px}.setup{padding-top:20px}.example-equation{font-size:43px;margin-bottom:17px}.setup h3{font-size:20px}.setup>p:not(.example-equation){font-size:15px}.setup .primary-button{margin-top:20px}.equation{font-size:47px;padding:18px 0 15px;letter-spacing:0}.equation .operator{padding:0 7px}#answer{height:59px;font-size:34px}.keypad button{min-height:54px;font-size:26px}.keypad{gap:8px}.keypad .submit-key{font-size:16px}.game-bottom{margin-top:14px}.result-stats{gap:6px}.result-stats strong{font-size:28px}.result-stats span{font-size:12px;letter-spacing:0}.result-stats>div{padding:15px 5px}.result-actions>button{flex:1;font-size:14px;padding-inline:10px}.leaderboard{padding:21px}.leaderboard select{font-size:14px}.leaderboard h2{font-size:26px}footer{flex-wrap:wrap;gap:10px}.preview-pill{width:100%;font-size:12px}dialog{padding:25px}.game .feedback{font-size:14px;min-height:31px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{transition:none!important}}

/* 2.1 — compact setup, pre-round countdown, focused play, and untimed practice. */
body[data-mode="setup"] .scoreboard,body[data-mode="setup"] .time-track{display:none}
.setup{padding:0}.setup .primary-button{margin-top:0}.setup .round-rules{font-size:14px;margin-top:14px;line-height:1.5}.setup .input-hint{margin-top:10px;font-size:12px!important}
.countdown{text-align:center;min-height:300px;padding:30px 0 12px;outline:none}.countdown>p{color:var(--muted);font-size:16px}.countdown>strong{display:block;color:var(--mint);font:500 100px/1.25 var(--display);margin:8px 0}.countdown .text-button{margin-top:12px}
.practice-progress{display:flex;justify-content:space-between;align-items:center;gap:15px;padding:14px 0;border-block:1px solid var(--line);margin-bottom:9px}.practice-progress span{font-size:12px;letter-spacing:1px;color:var(--mint)}.practice-progress strong{font-size:14px;font-weight:500}
.result-actions .practice-button{flex-basis:100%;width:100%}.practice-complete{padding:30px 0;outline:none}.practice-complete h2{font:500 34px/1.2 var(--display);margin:12px 0 18px}.practice-complete p{margin-bottom:14px}.practice-complete .primary-button{margin-top:12px}.game-bottom p{max-width:70%}.feedback.reveal{color:var(--coral);font-weight:600}
body[data-mode="practice"] .scoreboard,body[data-mode="practice"] .time-track{display:none}
@media(max-width:740px){body[data-mode="game"] .leaderboard,body[data-mode="countdown"] .leaderboard,body[data-mode="practice"] .leaderboard{display:none}}
@media(max-width:480px){.setup{padding:0}.setup .primary-button{margin-top:0}.setup .round-rules{font-size:14px}.play{padding:18px 16px}.countdown{min-height:280px;padding-top:20px}.countdown>strong{font-size:90px}.practice-progress{gap:10px}.practice-complete h2{font-size:30px}}

/* 2.3 — Mixed mode and compact overall/challenge leaderboard. */
.operation[data-operation="mixed"] .symbol{font-size:17px;white-space:nowrap;letter-spacing:1px}
.board-switch{display:grid;grid-template-columns:1fr 1fr;gap:6px;margin-bottom:12px}
.board-switch button{min-height:44px;padding:8px;border:1px solid #50616d;border-radius:8px;background:var(--key);font-size:14px;font-weight:600}
.board-switch button[aria-pressed="true"]{background:var(--mint);color:#142a20;border-color:var(--mint)}
.board-filters{display:grid;grid-template-columns:1fr;gap:8px}
.board-filters select{width:100%;margin:0;font-size:14px}
.leaderboard-heading{margin-bottom:12px}.leaderboard h2{font-size:25px}
.leaderboard-caption{font-size:14px;line-height:1.5;margin:13px 0 16px}
.ranking-head{padding:0 8px 8px}
.rankings li{grid-template-columns:22px minmax(0,1fr) auto;gap:8px;padding:6px 8px;border-radius:7px;margin-bottom:5px;min-height:52px}
.rank-number{font-size:15px}.rank-player{display:grid;gap:2px;min-width:0}
.rank-name{display:block;font-size:14px;line-height:1.25}
.rank-challenge{display:block;font-size:12px;line-height:1.25;color:var(--muted)}
.rank-score{font-size:20px;line-height:1}.rank-score small{font-size:12px;line-height:1.2;margin-top:2px}
.board-more{width:100%;min-height:44px;margin-top:7px;border:1px solid #50616d;border-radius:8px;background:var(--key);font-size:14px}
.board-more:hover:not(:disabled){background:#34464d}.board-more:disabled{opacity:.6;cursor:wait}
.your-best{margin-top:18px;padding-top:14px}.your-best strong{font-size:16px}.your-best small{font-size:13px;color:var(--muted)}
@media(min-width:741px) and (max-width:1050px){.operations{grid-template-columns:repeat(3,minmax(0,1fr))}.operation[data-operation="mixed"]{grid-column:span 2}}
@media(max-width:740px){.operation[data-operation="mixed"]{grid-column:1/-1}.board-filters{grid-template-columns:1fr 1fr}}
@media(max-width:480px){.level-example{font-size:12px;letter-spacing:-.2px}.rankings li{padding:6px 8px;min-height:52px}.leaderboard{padding:18px}.leaderboard h2{font-size:25px}}