:root{color-scheme:light dark;--ios-background: #ffffff;--ios-grouped-background: #f2f2f7;--ios-secondary-background: #f2f2f7;--ios-tertiary-background: #ffffff;--ios-label: #000000;--ios-secondary-label: #8a8a8e;--ios-separator: rgba(60, 60, 67, .22);--ios-blue: #007aff;--ios-blue-soft: rgba(0, 122, 255, .18);--ios-green: #34c759;--ios-red: #ff3b30;--ios-orange: #ff9500;--ios-gray: #8e8e93;--glass-fill: rgba(242, 242, 247, .76);--glass-border: rgba(60, 60, 67, .18);--shadow-soft: 0 16px 38px rgba(0, 0, 0, .08);font-family:-apple-system,BlinkMacSystemFont,SF Pro Text,SF Pro Display,Segoe UI,sans-serif;background:var(--ios-background);color:var(--ios-label);font-synthesis:none;text-rendering:optimizeLegibility}*{box-sizing:border-box}body{margin:0;min-width:320px;min-height:100vh;overflow-x:hidden;background:var(--ios-background)}button,input{font:inherit}button{appearance:none}a{color:inherit}.app-shell{position:relative;width:min(430px,100%);min-height:100vh;margin:0 auto;padding:22px 12px 28px}.document-page{width:min(820px,100%);margin:0 auto;padding:28px 16px 64px}.top-bar{min-height:44px;display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:18px}.brand{min-height:38px;border:0;background:transparent;color:var(--ios-label);display:inline-flex;align-items:center;gap:9px;padding:0;font-size:1rem;font-weight:700;text-decoration:none;cursor:pointer}.brand img{width:30px;height:30px;border-radius:7px;box-shadow:0 4px 10px #0000001f}.site-nav,.page-nav{display:flex;align-items:center;gap:8px;color:var(--ios-label);font-size:.94rem;font-weight:650}.site-nav a,.site-nav button,.page-nav a{min-height:36px;border:1px solid var(--glass-border);border-radius:999px;background:var(--glass-fill);color:inherit;display:inline-flex;align-items:center;justify-content:center;padding:8px 13px;text-decoration:none;box-shadow:0 7px 16px #0000000a;-webkit-backdrop-filter:blur(22px) saturate(1.3);backdrop-filter:blur(22px) saturate(1.3);cursor:pointer}.settings-panel{position:absolute;top:70px;right:12px;z-index:20;width:min(380px,calc(100% - 24px));margin:0;border:1px solid var(--glass-border);border-radius:20px;background:linear-gradient(180deg,#ffffffad,#ffffff47),var(--glass-fill);display:grid;gap:12px;padding:12px;box-shadow:var(--shadow-soft);-webkit-backdrop-filter:blur(22px) saturate(1.3);backdrop-filter:blur(22px) saturate(1.3)}.settings-header{display:flex;align-items:baseline;justify-content:space-between;gap:12px;padding:2px 4px 0}.settings-header h2{margin:0;color:var(--ios-label);font-size:1.05rem;line-height:1.2}.settings-header span{color:var(--ios-secondary-label);font-size:.78rem;font-weight:650;white-space:nowrap}.settings-group{border:1px solid var(--ios-separator);border-radius:16px;background:var(--ios-tertiary-background);overflow:hidden}.settings-row{min-width:0;border:0;display:flex;align-items:center;justify-content:space-between;gap:12px;margin:0;padding:11px 12px}.settings-row+.settings-row{border-top:1px solid var(--ios-separator)}.settings-row legend{width:96px;color:var(--ios-secondary-label);float:left;font-size:.86rem;font-weight:700}.segmented-control{border:1px solid var(--ios-separator);border-radius:999px;background:var(--ios-secondary-background);display:grid;grid-auto-columns:1fr;grid-auto-flow:column;flex:1;min-width:0;padding:2px}.segmented-control label{min-width:0}.segmented-control input{position:absolute;opacity:0;pointer-events:none}.segmented-control span{min-height:30px;border-radius:999px;color:var(--ios-secondary-label);display:grid;place-items:center;padding:7px 10px;font-size:.84rem;font-weight:650;cursor:pointer}.segmented-control input:checked+span{background:var(--ios-blue);color:var(--ios-label);box-shadow:0 6px 12px #007aff33}:root:not([data-theme=dark]) .segmented-control input:checked+span{color:#fff}.start-shell{display:flex;flex-direction:column}.start-panel{flex:1;display:grid;align-items:center}.start-card{display:grid;gap:26px;justify-items:stretch;padding:10px 0 36px}.start-copy{display:grid;gap:12px;justify-items:center;text-align:center}h1{margin:0;color:var(--ios-label);font-size:2.625rem;font-weight:700;line-height:1.04;letter-spacing:-.02em}.start-date{margin:0;color:var(--ios-secondary-label);font-size:1.25rem;font-weight:650}.start-subtitle{width:min(320px,100%);margin:-8px auto 0;color:var(--ios-secondary-label);font-size:1rem;line-height:1.42;text-align:center}.start-secondary-actions{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;padding-inline:12px}.start-secondary-actions button{min-height:50px;border:1px solid var(--glass-border);border-radius:16px;background:var(--glass-fill);color:var(--ios-label);display:grid;place-items:center;padding:14px 12px;font-size:.95rem;font-weight:650;text-align:center;text-decoration:none;box-shadow:0 8px 18px #0000000a;-webkit-backdrop-filter:blur(22px) saturate(1.3);backdrop-filter:blur(22px) saturate(1.3);cursor:pointer}.start-secondary-actions button[aria-pressed=true]{border-color:#007aff59;background:var(--ios-blue-soft)}.start-info-card{width:min(320px,calc(100% - 24px));justify-self:center;border-radius:16px;background:var(--ios-secondary-background);color:var(--ios-label);display:grid;gap:5px;padding:14px 16px;text-align:left}.start-info-card strong{font-size:.95rem}.start-info-card span{color:var(--ios-secondary-label);font-size:.9rem;line-height:1.4}.play-button{min-height:60px;border:1px solid rgba(52,199,89,.35);border-radius:18px;background:var(--ios-green);color:#fff;font-size:1.06rem;font-weight:700;margin-inline:12px;box-shadow:0 14px 24px #34c7593d;cursor:pointer}.date-picker{display:grid;gap:7px;color:var(--ios-secondary-label);font-size:.78rem;font-weight:700}.start-date-picker{width:min(320px,calc(100% - 24px));justify-self:center}.date-picker input{min-height:38px;border:1px solid var(--ios-separator);border-radius:10px;background:var(--ios-tertiary-background);color:var(--ios-label);padding:8px 11px}.digit-rail{display:flex;align-items:center;justify-content:center;gap:8px;margin:0;padding-inline:0}.digit-rail span{width:40px;height:40px;display:grid;place-items:center;border-radius:8px;border:1px solid rgba(142,142,147,.3);background:var(--ios-secondary-background);color:var(--ios-secondary-label);font-size:1.5rem;font-weight:700;line-height:1}.digit-rail span.used{opacity:.5}.digit-rail span.active{color:var(--ios-label);border-color:var(--ios-blue);background:var(--ios-blue-soft);box-shadow:inset 0 0 0 2px var(--ios-blue)}.digit-rail i{width:auto;height:auto;background:transparent;color:var(--ios-secondary-label);font-style:normal;font-weight:700;font-size:1.45rem}.digit-rail i:before{content:"/"}.start-digits span{color:var(--ios-secondary-label);background:var(--ios-secondary-background);border-color:#8e8e934d;box-shadow:none}.play-shell{width:min(430px,100%)}.game-panel{display:grid;gap:10px;padding:0}.game-heading{display:grid;gap:12px;margin-bottom:6px}.game-heading h1{font-size:1.8rem}.game-heading p{margin:6px 0 0;color:var(--ios-secondary-label);line-height:1.5}.equation-box{min-height:64px;border-radius:12px;border:1px solid transparent;background:var(--ios-secondary-background);display:flex;align-items:center;justify-content:center;padding:12px 16px;font-family:Georgia,Times New Roman,serif;font-size:1.75rem;overflow-x:auto;white-space:nowrap}.cursor{width:2px;height:28px;margin-left:3px;border-radius:999px;background:var(--ios-blue);animation:blink 1.05s steps(2,start) infinite}@keyframes blink{50%{opacity:0}}.helper-row{display:flex;justify-content:space-between;gap:16px;margin:0 16px}.helper-row span{min-height:34px;border-radius:8px;background:var(--glass-fill);color:var(--ios-label);display:inline-flex;align-items:center;padding:8px 12px;font-family:ui-rounded,SF Pro Rounded,ui-monospace,SFMono-Regular,Menlo,monospace;font-size:.98rem;font-weight:650;box-shadow:0 8px 18px #0000000a;-webkit-backdrop-filter:blur(22px) saturate(1.3);backdrop-filter:blur(22px) saturate(1.3)}.next-digit{width:90px;height:70px;display:block;margin:4px auto 8px;border:1px solid rgba(0,122,255,.35);border-radius:14px;background:var(--ios-blue);color:#fff;font-size:2.25rem;font-weight:700;box-shadow:0 14px 28px #007aff3d;cursor:pointer}.next-digit:disabled{background:var(--ios-gray);border-color:#8e8e9359;box-shadow:none;cursor:not-allowed}.operator-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px}.operator-grid button{min-height:70px;border:1px solid rgba(142,142,147,.25);border-radius:14px;background:var(--ios-tertiary-background);color:var(--ios-label);font-size:1.95rem;font-weight:650;cursor:pointer}.operator-grid .wide,.operator-grid .submit{min-height:60px;grid-column:span 2;border-radius:12px}.operator-grid .submit{border-color:#34c75959;background:var(--ios-green);color:#fff;font-size:1.3rem;font-weight:700}.operator-grid .danger{color:var(--ios-red);border-color:#ff3b3047;background:#ff3b3029}.operator-grid .warning{color:var(--ios-orange);border-color:#ff950047;background:#ff950029}.operator-grid button:hover,.next-digit:hover,.play-button:hover,.start-secondary-actions button:hover,.site-nav button:hover,.site-nav a:hover,.page-nav a:hover{transform:translateY(-1px)}.operator-grid button:active,.next-digit:active,.play-button:active,.start-secondary-actions button:active,.site-nav button:active{transform:scale(.96);opacity:.82}.status-message{margin:8px 0 0;color:var(--ios-green);font-weight:700}.status-message.error{color:var(--ios-red)}.solutions-panel{margin-top:20px;border-radius:18px;background:var(--ios-tertiary-background);padding:18px}.solutions-panel h2,.document-page h2{margin:0 0 12px}.solutions-panel p,.solutions-panel span,.document-page p,.document-page li,.meta{color:var(--ios-secondary-label);line-height:1.55}.solutions-panel ol{margin:0;padding-left:1.25rem}.solutions-panel li{margin-bottom:14px}.solutions-panel strong,.solutions-panel span{display:block}.solutions-panel span{margin-top:4px;font-size:.92rem}.document-page section{border-radius:18px;background:var(--ios-tertiary-background);padding:22px}.document-page h1{margin:42px 0 12px}@media(min-width:760px){.app-shell{padding-top:30px}.play-shell{width:min(480px,100%)}}@media(min-width:920px){.play-shell{width:min(980px,100%);display:grid;grid-template-columns:minmax(430px,480px) minmax(280px,1fr);align-items:start;column-gap:28px}.play-shell .top-bar{grid-column:1 / -1}.solutions-panel{margin-top:0;position:sticky;top:30px}}@media(max-width:520px){.brand span{display:none}}@media(max-width:380px){.site-nav{gap:6px;font-size:.88rem}.site-nav a{padding-inline:10px}.digit-rail{gap:6px}.digit-rail span{width:38px;height:38px}.operator-grid{gap:9px}.operator-grid button{min-height:64px}}@media(prefers-color-scheme:dark){:root{--ios-background: #000000;--ios-grouped-background: #000000;--ios-secondary-background: #1c1c1e;--ios-tertiary-background: #2c2c2e;--ios-label: #ffffff;--ios-secondary-label: #98989d;--ios-separator: rgba(84, 84, 88, .65);--ios-blue-soft: rgba(10, 132, 255, .22);--ios-blue: #0a84ff;--ios-green: #30d158;--ios-red: #ff453a;--ios-orange: #ff9f0a;--ios-gray: #8e8e93;--glass-fill: rgba(28, 28, 30, .72);--glass-border: rgba(84, 84, 88, .48);--shadow-soft: none}.brand img{box-shadow:none}.solutions-panel,.document-page section{background:var(--ios-secondary-background)}.settings-panel{background:linear-gradient(180deg,#2c2c2ee6,#1c1c1eb8),var(--glass-fill)}}:root[data-theme=dark]{color-scheme:dark;--ios-background: #000000;--ios-grouped-background: #000000;--ios-secondary-background: #1c1c1e;--ios-tertiary-background: #2c2c2e;--ios-label: #ffffff;--ios-secondary-label: #98989d;--ios-separator: rgba(84, 84, 88, .65);--ios-blue-soft: rgba(10, 132, 255, .22);--ios-blue: #0a84ff;--ios-green: #30d158;--ios-red: #ff453a;--ios-orange: #ff9f0a;--ios-gray: #8e8e93;--glass-fill: rgba(28, 28, 30, .72);--glass-border: rgba(84, 84, 88, .48);--shadow-soft: none}:root[data-theme=dark] .brand img{box-shadow:none}:root[data-theme=dark] .solutions-panel,:root[data-theme=dark] .document-page section{background:var(--ios-secondary-background)}:root[data-theme=dark] .settings-panel{background:linear-gradient(180deg,#2c2c2ee6,#1c1c1eb8),var(--glass-fill)}:root[data-theme=light]{color-scheme:light;--ios-background: #ffffff;--ios-grouped-background: #f2f2f7;--ios-secondary-background: #f2f2f7;--ios-tertiary-background: #ffffff;--ios-label: #000000;--ios-secondary-label: #8a8a8e;--ios-separator: rgba(60, 60, 67, .22);--ios-blue: #007aff;--ios-blue-soft: rgba(0, 122, 255, .18);--ios-green: #34c759;--ios-red: #ff3b30;--ios-orange: #ff9500;--ios-gray: #8e8e93;--glass-fill: rgba(242, 242, 247, .76);--glass-border: rgba(60, 60, 67, .18);--shadow-soft: 0 16px 38px rgba(0, 0, 0, .08)}:root[data-theme=light] .brand img{box-shadow:0 4px 10px #0000001f}:root[data-theme=light] .solutions-panel,:root[data-theme=light] .document-page section{background:var(--ios-tertiary-background)}:root[data-theme=light] .settings-panel{background:linear-gradient(180deg,#ffffffad,#ffffff47),var(--glass-fill)}