:root{--bg-body:#0a0a14;--bg-primary:#0f0f1a;--bg-secondary:#161628;--bg-cell:#1a1a30;--bg-cell-hover:#22223a;--bg-cell-selected:#2a2a50;--bg-cell-highlight:#1e1e3a;--bg-cell-same-number:#252548;--bg-glass:#161628a6;--bg-glass-strong:#161628d9;--accent-primary:#7c6aff;--accent-primary-soft:#7c6aff26;--accent-primary-glow:#7c6aff59;--accent-secondary:#00d4aa;--accent-secondary-soft:#00d4aa1f;--accent-error:#ff5c6c;--accent-error-soft:#ff5c6c26;--accent-success:#44e08a;--accent-warning:#ffb84d;--text-primary:#e8e8f4;--text-secondary:#8888a8;--text-muted:#55556e;--text-given:#fff;--text-user:var(--accent-primary);--text-notes:var(--text-secondary);--text-error:var(--accent-error);--border-cell:#ffffff0f;--border-box:#ffffff2e;--border-outer:#7c6aff66;--border-glass:#ffffff14;--font-ui:"Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;--font-mono:"JetBrains Mono", "Fira Code", "Consolas", monospace;--fs-xs:.7rem;--fs-sm:.8rem;--fs-base:.95rem;--fs-md:1.1rem;--fs-lg:1.35rem;--fs-xl:1.6rem;--fs-2xl:2rem;--fs-cell:clamp(1.1rem, 3.5vw, 1.5rem);--fs-cell-note:clamp(.5rem, 1.5vw, .65rem);--space-xs:4px;--space-sm:8px;--space-md:12px;--space-lg:16px;--space-xl:24px;--space-2xl:32px;--space-3xl:48px;--radius-sm:6px;--radius-md:10px;--radius-lg:14px;--radius-xl:20px;--radius-full:9999px;--shadow-sm:0 2px 8px #00000040;--shadow-md:0 4px 20px #00000059;--shadow-lg:0 8px 40px #00000073;--shadow-glow:0 0 20px var(--accent-primary-glow);--shadow-glow-sm:0 0 10px var(--accent-primary-glow);--ease-out:cubic-bezier(.16, 1, .3, 1);--ease-spring:cubic-bezier(.34, 1.56, .64, 1);--duration-fast:.12s;--duration-base:.2s;--duration-slow:.4s;--board-size:min(90vw, 460px);--cell-size:calc(var(--board-size) / 9)}*,:before,:after{box-sizing:border-box;margin:0;padding:0}html{-webkit-text-size-adjust:100%;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;font-size:16px}body{font-family:var(--font-ui);background:var(--bg-body);color:var(--text-primary);min-height:100dvh;padding:var(--space-lg);justify-content:center;align-items:flex-start;display:flex;position:relative;overflow-x:hidden}body:before,body:after{content:"";filter:blur(100px);opacity:.4;pointer-events:none;z-index:0;border-radius:50%;position:fixed}body:before{background:radial-gradient(circle, var(--accent-primary-glow), transparent 70%);width:400px;height:400px;animation:12s ease-in-out infinite alternate ambientFloat1;top:-100px;left:-100px}body:after{background:radial-gradient(circle,#00d4aa33,#0000 70%);width:350px;height:350px;animation:15s ease-in-out infinite alternate ambientFloat2;bottom:-80px;right:-80px}::selection{background:var(--accent-primary-soft);color:var(--text-primary)}:focus-visible{outline:2px solid var(--accent-primary);outline-offset:2px}::-webkit-scrollbar{width:6px}::-webkit-scrollbar-track{background:0 0}::-webkit-scrollbar-thumb{background:var(--text-muted);border-radius:var(--radius-full)}button{cursor:pointer;color:inherit;font-family:inherit;font-size:inherit;-webkit-tap-highlight-color:transparent;background:0 0;border:none;line-height:1}select{cursor:pointer;-webkit-tap-highlight-color:transparent;font-family:inherit}label{font-family:var(--font-ui);font-size:var(--fs-sm);color:var(--text-secondary);letter-spacing:.02em;font-weight:500}#game-container{z-index:1;align-items:center;gap:var(--space-xl);width:100%;max-width:520px;padding:var(--space-xl);margin-top:var(--space-lg);background:var(--bg-glass);-webkit-backdrop-filter:blur(20px);border:1px solid var(--border-glass);border-radius:var(--radius-xl);box-shadow:var(--shadow-lg);flex-direction:column;display:flex;position:relative}#controls{justify-content:space-between;align-items:center;gap:var(--space-md);flex-wrap:wrap;order:-1;width:100%;display:flex}#sudoku-grid{width:var(--board-size);height:var(--board-size);border:2px solid var(--border-outer);border-radius:var(--radius-md);box-shadow:var(--shadow-glow), var(--shadow-md);background:var(--border-cell);flex-shrink:0;grid-template-rows:repeat(9,1fr);grid-template-columns:repeat(9,1fr);display:grid;overflow:hidden}#message{text-align:center;width:100%;min-height:0;font-size:var(--fs-sm);color:var(--accent-secondary);transition:opacity var(--duration-base) var(--ease-out), color var(--duration-base) var(--ease-out);font-weight:500;overflow:hidden}#message:empty{display:none}#message.message--error{color:var(--accent-error)}#message.message--success{color:var(--accent-success)}#numpad{gap:var(--space-xs);grid-template-columns:repeat(9,1fr);width:100%;display:grid}#action-bar{justify-content:center;gap:var(--space-sm);width:100%;display:flex}@media (width<=480px){body{padding:var(--space-sm)}#game-container{padding:var(--space-md);gap:var(--space-md);border-radius:var(--radius-lg);margin-top:var(--space-sm)}#controls{gap:var(--space-sm)}}@media (width>=600px){body{align-items:center}#game-container{margin-top:0}}.cell{background:var(--bg-cell);font-family:var(--font-mono);font-size:var(--fs-cell);color:var(--text-user);cursor:pointer;transition:background var(--duration-fast) var(--ease-out), color var(--duration-fast) var(--ease-out);-webkit-user-select:none;user-select:none;justify-content:center;align-items:center;font-weight:600;display:flex;position:relative}.cell--border-right{border-right:2px solid var(--border-box)!important}.cell--border-bottom{border-bottom:2px solid var(--border-box)!important}.cell:hover{background:var(--bg-cell-hover)}.cell--selected{box-shadow:inset 0 0 0 2px var(--accent-primary), var(--shadow-glow-sm);z-index:2;border-radius:6px;background:var(--bg-cell-selected)!important}.cell--highlighted{background:var(--bg-cell-highlight)!important}.cell--same-number{color:var(--accent-secondary);background:var(--bg-cell-same-number)!important}.cell--given{color:var(--text-given);cursor:default;font-weight:700}.cell--error{animation:cellShake .4s var(--ease-out);color:var(--text-error)!important;background:var(--accent-error-soft)!important}.cell--success{animation:cellPop .3s var(--ease-spring)}.cell__notes{grid-template-rows:repeat(3,1fr);grid-template-columns:repeat(3,1fr);width:100%;height:100%;padding:2px;display:grid}.cell__note{font-family:var(--font-mono);font-size:var(--fs-cell-note);color:var(--text-notes);justify-content:center;align-items:center;font-weight:500;display:flex}#new-game-btn{padding:var(--space-sm) var(--space-lg);background:linear-gradient(135deg, var(--accent-primary), #6354e0);color:#fff;font-size:var(--fs-sm);border-radius:var(--radius-full);letter-spacing:.03em;transition:transform var(--duration-base) var(--ease-out), box-shadow var(--duration-base) var(--ease-out), filter var(--duration-base) var(--ease-out);white-space:nowrap;font-weight:600;box-shadow:0 2px 12px #7c6aff4d}#new-game-btn:hover{filter:brightness(1.1);transform:translateY(-1px);box-shadow:0 4px 20px #7c6aff73}#new-game-btn:active{transform:translateY(0)scale(.97)}#difficulty-controls{align-items:center;gap:var(--space-sm);display:flex}#difficulty{background:var(--bg-secondary);color:var(--text-primary);border:1px solid var(--border-glass);border-radius:var(--radius-sm);font-size:var(--fs-sm);appearance:none;transition:border-color var(--duration-base) var(--ease-out), box-shadow var(--duration-base) var(--ease-out);background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%238888a8' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");background-position:right 8px center;background-repeat:no-repeat;padding:6px 28px 6px 10px;font-weight:500}#difficulty:hover{border-color:var(--accent-primary)}#difficulty:focus{border-color:var(--accent-primary);box-shadow:0 0 0 3px var(--accent-primary-soft);outline:none}#difficulty option{background:var(--bg-primary);color:var(--text-primary)}#timer{font-family:var(--font-mono);font-size:var(--fs-md);color:var(--text-primary);background:var(--bg-secondary);border:1px solid var(--border-glass);border-radius:var(--radius-sm);letter-spacing:.08em;text-align:center;min-width:80px;padding:6px 14px;font-weight:600;position:relative;overflow:hidden}#timer:before{content:"";background:linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));opacity:.7;height:2px;position:absolute;top:0;left:0;right:0}#validation-controls{align-items:center;gap:var(--space-sm);display:flex}#validate-moves{appearance:none;background:var(--bg-secondary);border:1px solid var(--border-glass);border-radius:var(--radius-full);cursor:pointer;width:38px;height:20px;transition:background-color var(--duration-base) var(--ease-out), border-color var(--duration-base) var(--ease-out);position:relative}#validate-moves:after{content:"";background:var(--text-secondary);width:14px;height:14px;transition:transform var(--duration-base) var(--ease-spring), background-color var(--duration-base) var(--ease-spring);border-radius:50%;position:absolute;top:2px;left:2px}#validate-moves:checked{background:var(--accent-primary);border-color:var(--accent-primary)}#validate-moves:checked:after{background:#fff;transform:translate(18px)}.numpad-btn{aspect-ratio:1;font-family:var(--font-mono);font-size:var(--fs-lg);color:var(--text-primary);background:var(--bg-secondary);border:1px solid var(--border-glass);border-radius:var(--radius-md);transition:transform var(--duration-base) var(--ease-out), box-shadow var(--duration-base) var(--ease-out), border-color var(--duration-base) var(--ease-out);justify-content:center;align-items:center;font-weight:700;display:flex;position:relative}.numpad-btn:hover{border-color:var(--accent-primary);box-shadow:var(--shadow-glow-sm);transform:translateY(-2px)}.numpad-btn:active{transform:translateY(0)scale(.95)}.numpad-btn--completed{opacity:.3;pointer-events:none}.action-btn{padding:var(--space-sm) var(--space-md);color:var(--text-secondary);border-radius:var(--radius-md);transition:transform var(--duration-base) var(--ease-out), color var(--duration-base) var(--ease-out), background-color var(--duration-base) var(--ease-out);flex-direction:column;align-items:center;gap:4px;min-width:56px;display:flex}.action-btn:hover{color:var(--text-primary);background:var(--bg-secondary)}.action-btn:active{transform:scale(.93)}.action-btn--active{background:var(--accent-primary-soft);color:var(--accent-primary)!important}.action-btn__label{font-size:var(--fs-xs);font-weight:500}.message--visible{padding:var(--space-sm) var(--space-md);background:var(--accent-secondary-soft);border-radius:var(--radius-sm);animation:fadeSlideUp .3s var(--ease-out);border:1px solid #00d4aa33}.modal-overlay{z-index:100;opacity:0;pointer-events:none;transition:opacity var(--duration-base) var(--ease-out);-webkit-backdrop-filter:blur(3px);background:#0a0a0f4d;justify-content:center;align-items:center;display:flex;position:fixed;inset:0}.modal-overlay--visible{opacity:1;pointer-events:auto}.modal-content{-webkit-backdrop-filter:blur(20px);text-align:center;color:var(--text-primary);background:#1e1e28a6;border:1px solid #ffffff1a;border-radius:16px;width:340px;max-width:90%;padding:24px;transition:transform .4s cubic-bezier(.175,.885,.32,1.275);transform:translateY(20px)scale(.95);box-shadow:0 8px 32px #0006}.modal-overlay--visible .modal-content{transform:translateY(0)scale(1)}.modal-title{font-size:var(--fs-lg);color:#fff;margin-bottom:12px;font-weight:700}.modal-text{font-size:var(--fs-sm);color:var(--text-secondary);margin-bottom:24px;line-height:1.5}.modal-buttons{justify-content:center;gap:12px;display:flex}.btn-secondary{color:var(--text-primary);border-radius:var(--radius-md);cursor:pointer;background:#ffffff0d;border:1px solid #ffffff1a;flex:1;padding:10px 16px;font-weight:500;transition:background .2s}.btn-secondary:hover{background:#ffffff1a}.btn-primary{background:var(--accent-primary);color:#fff;border-radius:var(--radius-md);cursor:pointer;border:none;flex:1;padding:10px 16px;font-weight:600;transition:filter .2s,transform .2s}.btn-primary:hover{filter:brightness(1.1);transform:translateY(-1px)}.btn-primary:active{transform:translateY(0)scale(.98)}.board--blurred{filter:blur(6px)grayscale(.2);pointer-events:none;transition:filter .4s var(--ease-out)}@keyframes ambientFloat1{0%{transform:translate(0)scale(1)}to{transform:translate(60px,40px)scale(1.15)}}@keyframes ambientFloat2{0%{transform:translate(0)scale(1)}to{transform:translate(-50px,-30px)scale(1.1)}}@keyframes cellShake{0%,to{transform:translate(0)}20%{transform:translate(-3px)}40%{transform:translate(3px)}60%{transform:translate(-2px)}80%{transform:translate(2px)}}@keyframes cellPop{0%{transform:scale(1)}50%{transform:scale(1.15)}to{transform:scale(1)}}@keyframes fadeSlideUp{0%{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}@keyframes fadeIn{0%{opacity:0}to{opacity:1}}@keyframes boardReveal{0%{opacity:0;transform:scale(.95)}to{opacity:1;transform:scale(1)}}@keyframes numberPlace{0%{opacity:0;transform:scale(.5)}60%{transform:scale(1.1)}to{opacity:1;transform:scale(1)}}#sudoku-grid{animation:boardReveal .5s var(--ease-out) both}.cell--animate-in{animation:fadeIn .2s var(--ease-out) both}.cell--number-placed{animation:numberPlace .25s var(--ease-spring)}#controls{animation:fadeSlideUp .4s var(--ease-out) .15s both}#numpad{animation:fadeSlideUp .4s var(--ease-out) .25s both}#action-bar{animation:fadeSlideUp .4s var(--ease-out) .2s both}