:root{--accent: #6366f1;--accent-hover: #818cf8;--accent-dim: rgba(99, 102, 241, .15);--bg: #0a0a0a;--bg-card: rgba(255, 255, 255, .04);--bg-card-hover: rgba(255, 255, 255, .07);--border: rgba(255, 255, 255, .1);--border-active: rgba(99, 102, 241, .5);--text: #fafafa;--text-dim: rgba(255, 255, 255, .55);--text-mid: rgba(255, 255, 255, .75);--success: #22c55e;--error: #ef4444;color-scheme:dark;font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,sans-serif;line-height:1.5}*{box-sizing:border-box;margin:0}html,body,#root{min-height:100vh;background:var(--bg);color:var(--text)}.app{min-height:100vh;display:flex;flex-direction:column}.navbar{display:flex;align-items:center;justify-content:space-between;padding:.75rem 1.5rem;border-bottom:1px solid var(--border);background:#0a0a0ad9;-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);position:sticky;top:0;z-index:100}.nav-brand{font-size:1.1rem;font-weight:700;letter-spacing:-.02em;background:linear-gradient(135deg,var(--accent),var(--accent-hover));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.nav-tabs{display:flex;gap:.25rem}.nav-tab{background:none;border:none;color:var(--text-dim);padding:.5rem 1rem;border-radius:.5rem;cursor:pointer;font-size:.875rem;font-weight:500;transition:all .15s}.nav-tab:hover{color:var(--text);background:var(--bg-card)}.nav-tab.active{color:var(--accent);background:var(--accent-dim)}.main-content{flex:1;max-width:1100px;width:100%;margin:0 auto;padding:2rem 1.5rem}.btn{padding:.65rem 1.5rem;border-radius:.5rem;border:1px solid var(--border);font-size:.9rem;font-weight:500;cursor:pointer;transition:all .15s;background:var(--bg-card);color:var(--text)}.btn:hover:not(:disabled){background:var(--bg-card-hover);border-color:var(--border-active)}.btn:disabled{opacity:.35;cursor:default}.btn-primary{background:var(--accent);border-color:var(--accent);color:#fff}.btn-primary:hover:not(:disabled){background:var(--accent-hover);border-color:var(--accent-hover)}.btn-secondary{background:var(--accent-dim);border-color:var(--border-active);color:var(--accent-hover)}.btn-small{padding:.4rem 1rem;font-size:.8rem}.btn-ghost{background:transparent;border-color:transparent;color:var(--text-dim)}.btn-ghost:hover{color:var(--text);background:var(--bg-card)}.section-header{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:1rem;margin-bottom:1.5rem}.section-header h2{font-size:1.5rem;font-weight:600;letter-spacing:-.02em}.section-sub{color:var(--text-dim);font-size:.95rem;margin-top:.25rem}.home-view{text-align:center}.hero{padding:3rem 0}.hero-sign{margin-bottom:1.5rem;display:flex;justify-content:center}.hero h1{font-size:2.25rem;font-weight:700;letter-spacing:-.03em;margin-bottom:.75rem;background:linear-gradient(135deg,var(--text) 0%,var(--accent-hover) 100%);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.hero-sub{color:var(--text-dim);font-size:1.1rem;max-width:28rem;margin:0 auto 2rem}.hero-actions{display:flex;gap:.75rem;justify-content:center;flex-wrap:wrap}.stats-row{display:flex;justify-content:center;gap:1.5rem;margin:3rem 0;flex-wrap:wrap}.stat-card{display:flex;flex-direction:column;align-items:center;gap:.25rem;padding:1.25rem 2rem;background:var(--bg-card);border:1px solid var(--border);border-radius:.75rem;min-width:120px}.stat-number{font-size:2rem;font-weight:700;color:var(--accent-hover)}.stat-label{font-size:.8rem;color:var(--text-dim);text-transform:uppercase;letter-spacing:.1em}.preview-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(110px,1fr));gap:.75rem;max-width:500px;margin:0 auto}.preview-card{display:flex;flex-direction:column;align-items:center;gap:.5rem;padding:1rem .5rem;background:var(--bg-card);border:1px solid var(--border);border-radius:.75rem;cursor:pointer;transition:all .15s}.preview-card:hover{border-color:var(--border-active);background:var(--bg-card-hover);transform:translateY(-2px)}.preview-letter{font-size:1rem;font-weight:600;color:var(--text-mid)}.preview-hint{color:var(--text-dim);font-size:.85rem;margin-top:1rem}.search-input{padding:.5rem 1rem;border:1px solid var(--border);border-radius:.5rem;background:var(--bg-card);color:var(--text);font-size:.9rem;width:200px;outline:none;transition:border-color .15s}.search-input:focus{border-color:var(--border-active)}.search-input::placeholder{color:var(--text-dim)}.learn-layout{display:grid;grid-template-columns:1fr;gap:1.5rem}@media(min-width:768px){.learn-layout{grid-template-columns:1fr 1fr}}.alphabet-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(90px,1fr));gap:.5rem;align-content:start}.letter-card{display:flex;flex-direction:column;align-items:center;gap:.35rem;padding:.6rem .25rem;background:var(--bg-card);border:1px solid var(--border);border-radius:.6rem;cursor:pointer;transition:all .15s;color:var(--text)}.letter-card:hover{border-color:var(--border-active);background:var(--bg-card-hover)}.letter-card.selected{border-color:var(--accent);background:var(--accent-dim);box-shadow:0 0 0 1px var(--accent)}.letter-label{font-size:.85rem;font-weight:600;color:var(--text-mid)}.detail-panel{background:var(--bg-card);border:1px solid var(--border);border-radius:.75rem;padding:1.5rem;position:sticky;top:5rem;align-self:start}.detail-header{display:flex;align-items:center;gap:1.5rem;margin-bottom:1.5rem}.detail-title{display:flex;flex-direction:column}.detail-letter{font-size:3rem;font-weight:800;line-height:1;color:var(--accent-hover)}.detail-subtitle{font-size:.8rem;color:var(--text-dim);text-transform:uppercase;letter-spacing:.1em;margin-top:.25rem}.detail-body h3{font-size:.75rem;text-transform:uppercase;letter-spacing:.1em;color:var(--text-dim);margin-bottom:.5rem}.detail-section{margin-bottom:1.25rem}.detail-section p{font-size:.95rem;color:var(--text-mid);line-height:1.6}.tip-text{padding:.75rem 1rem;background:var(--accent-dim);border-radius:.5rem;border-left:3px solid var(--accent)}.detail-nav{display:flex;align-items:center;justify-content:space-between;margin-top:1.5rem;padding-top:1rem;border-top:1px solid var(--border)}.detail-counter{font-size:.8rem;color:var(--text-dim)}.flashcard-controls{display:flex;gap:.5rem}.flashcard-progress{margin-bottom:1.5rem}.progress-bar{height:4px;background:var(--bg-card);border-radius:2px;overflow:hidden;margin-bottom:.5rem}.progress-fill{height:100%;background:var(--accent);border-radius:2px;transition:width .3s ease}.progress-text{font-size:.8rem;color:var(--text-dim)}.flashcard{perspective:1000px;height:380px;max-width:500px;margin:0 auto 2rem;cursor:pointer}.flashcard-inner{width:100%;height:100%;transition:transform .5s cubic-bezier(.4,0,.2,1);transform-style:preserve-3d;position:relative}.flashcard.flipped .flashcard-inner{transform:rotateY(180deg)}.flashcard-front,.flashcard-back{position:absolute;top:0;right:0;bottom:0;left:0;backface-visibility:hidden;border:1px solid var(--border);border-radius:1rem;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:2rem;background:var(--bg-card)}.flashcard-front{gap:1.5rem}.flashcard-hint{font-size:.8rem;color:var(--text-dim)}.flashcard-back{transform:rotateY(180deg);gap:1rem;text-align:center}.flashcard-letter{font-size:4rem;font-weight:800;color:var(--accent-hover);line-height:1}.flashcard-desc{font-size:1rem;color:var(--text-mid);line-height:1.6}.flashcard-tip{font-size:.85rem;color:var(--text-dim);padding:.5rem 1rem;background:var(--accent-dim);border-radius:.5rem}.flashcard-nav{display:flex;align-items:center;justify-content:space-between;max-width:500px;margin:0 auto}.flashcard-dots{display:flex;gap:.35rem}.dot{width:2rem;height:2rem;border-radius:50%;border:1px solid var(--border);background:var(--bg-card);color:var(--text-dim);font-size:.7rem;cursor:pointer;transition:all .15s;display:flex;align-items:center;justify-content:center}.dot:hover{border-color:var(--border-active)}.dot.active{background:var(--accent);border-color:var(--accent);color:#fff}.dot.visited{background:var(--accent-dim);border-color:var(--border-active);color:var(--accent-hover)}.keyboard-hint{text-align:center;font-size:.75rem;color:var(--text-dim);margin-top:1.5rem}.quiz-modes{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:1rem}.quiz-mode-card{display:flex;flex-direction:column;align-items:center;gap:1rem;padding:2rem 1.5rem;background:var(--bg-card);border:1px solid var(--border);border-radius:.75rem;cursor:pointer;transition:all .2s;color:var(--text);text-align:center}.quiz-mode-card:hover{border-color:var(--border-active);background:var(--bg-card-hover);transform:translateY(-2px)}.mode-icon{width:100px;height:100px;display:flex;align-items:center;justify-content:center;background:var(--accent-dim);border-radius:50%}.mode-letter{font-size:2.5rem;font-weight:800;color:var(--accent-hover)}.quiz-mode-card h3{font-size:1.1rem;font-weight:600}.quiz-mode-card p{font-size:.85rem;color:var(--text-dim)}.quiz-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:1rem}.quiz-progress-text{font-size:.85rem;color:var(--text-dim)}.quiz-score{font-size:.85rem;font-weight:600;color:var(--accent-hover)}.quiz-question{text-align:center;padding:2rem 0}.quiz-instruction{font-size:1rem;color:var(--text-dim);margin-bottom:1.5rem}.quiz-sign-display{display:flex;justify-content:center;margin-bottom:2rem}.quiz-big-letter{font-size:5rem;font-weight:800;color:var(--accent-hover);display:block;margin-bottom:2rem}.quiz-options{display:flex;justify-content:center;gap:.75rem;flex-wrap:wrap}.quiz-options-grid{display:grid;grid-template-columns:repeat(2,1fr);max-width:400px;margin:0 auto;gap:.75rem}.quiz-option{min-width:4rem;padding:1rem 2rem;background:var(--bg-card);border:2px solid var(--border);border-radius:.75rem;font-size:1.5rem;font-weight:700;color:var(--text);cursor:pointer;transition:all .15s}.quiz-option:hover:not(:disabled){border-color:var(--border-active);background:var(--bg-card-hover)}.quiz-option.correct{border-color:var(--success);background:#22c55e26;color:var(--success)}.quiz-option.wrong{border-color:var(--error);background:#ef444426;color:var(--error)}.quiz-option-sign{padding:.75rem;background:var(--bg-card);border:2px solid var(--border);border-radius:.75rem;cursor:pointer;transition:all .15s;display:flex;align-items:center;justify-content:center}.quiz-option-sign:hover:not(:disabled){border-color:var(--border-active);background:var(--bg-card-hover)}.quiz-option-sign.correct{border-color:var(--success);background:#22c55e26}.quiz-option-sign.wrong{border-color:var(--error);background:#ef444426}.quiz-feedback{margin-top:1.5rem;padding:.75rem 1.25rem;border-radius:.5rem;font-size:.95rem;font-weight:500;max-width:400px;margin-left:auto;margin-right:auto}.quiz-feedback.right{background:#22c55e1f;color:var(--success);border:1px solid rgba(34,197,94,.3)}.quiz-feedback.wrong{background:#ef44441f;color:var(--error);border:1px solid rgba(239,68,68,.3)}.word-display{display:flex;justify-content:center;gap:.5rem;margin:1.5rem 0 .5rem}.word-letter{width:3rem;height:3.5rem;display:flex;align-items:center;justify-content:center;font-size:1.75rem;font-weight:700;border:2px solid var(--border);border-radius:.5rem;background:var(--bg-card);color:var(--text-dim);transition:all .2s}.word-letter.current{border-color:var(--accent);color:var(--accent-hover);background:var(--accent-dim);box-shadow:0 0 12px #6366f140}.word-letter.done{border-color:var(--success);color:var(--success);background:#22c55e1a}.word-hint{text-align:center;font-size:.85rem;color:var(--text-dim);margin-bottom:1.5rem}.quiz-result{text-align:center;padding:3rem 0}.result-ring{width:140px;height:140px;border-radius:50%;border:6px solid var(--error);display:flex;align-items:center;justify-content:center;margin:0 auto 1.5rem;transition:border-color .3s}.result-ring.pass{border-color:var(--success)}.result-score{font-size:2.5rem;font-weight:800}.quiz-result h2{font-size:1.5rem;margin-bottom:.5rem}.quiz-result p{color:var(--text-dim);margin-bottom:2rem}.result-actions{display:flex;gap:.75rem;justify-content:center}@media(max-width:640px){.hero h1{font-size:1.6rem}.main-content{padding:1.25rem 1rem}.flashcard{height:320px}.detail-header{flex-direction:column;text-align:center}.quiz-options-grid{grid-template-columns:repeat(2,1fr)}.nav-tabs{gap:0}.nav-tab{padding:.4rem .6rem;font-size:.75rem}.stats-row{gap:.75rem}.stat-card{padding:1rem 1.25rem;min-width:90px}}