:root{--bg-start: #f7f7f2;--bg-end: #e8efe1;--panel: rgba(255, 255, 255, .8);--card-front: #fffdf7;--card-back: #fffaf0;--text-main: #243121;--text-muted: #5d6d58;--accent: #567a47;--accent-strong: #3d5d31;--border: rgba(86, 122, 71, .15);--shadow: 0 16px 48px rgba(54, 73, 46, .14);--blank-bg: rgba(255, 211, 92, .28);--blank-border: rgba(194, 136, 0, .65);--answer-bg: linear-gradient(120deg, rgba(154, 208, 121, .5), rgba(255, 232, 156, .75))}*{box-sizing:border-box}html,body,#app{min-height:100%}body{margin:0;font-family:Inter,PingFang SC,Microsoft YaHei,sans-serif;color:var(--text-main);background:linear-gradient(135deg,var(--bg-start),var(--bg-end))}a{color:inherit}button{font:inherit}.page-shell{width:min(100%,960px);margin:0 auto;padding:48px 20px 64px}.home-page-shell{width:min(100%,1080px)}.hero{text-align:center;margin-bottom:28px}.home-hero{margin-bottom:18px}.eyebrow,.topic-eyebrow{margin:0 0 10px;color:var(--accent);font-weight:700;letter-spacing:.08em;text-transform:uppercase}.hero h1{margin:0;font-size:clamp(2rem,4vw,2.9rem)}.hero-copy,.topic-description{margin:12px auto 0;max-width:42rem;color:var(--text-muted);line-height:1.7}.app-panel,.topic-category-card{background:var(--panel);border:1px solid var(--border);border-radius:28px;box-shadow:var(--shadow);padding:24px;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px)}.topics-panel{padding:18px}.topics-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:12px}.topic-category-card{display:flex;align-items:center;justify-content:center;min-height:76px;padding:14px 12px;text-decoration:none;text-align:center;transition:transform .2s ease,box-shadow .2s ease,border-color .2s ease}.topic-category-card:hover,.topic-category-card:focus-visible,.nav-button:hover,.nav-button:focus-visible,.card-shell:focus-visible{outline:none;transform:translateY(-1px);box-shadow:0 10px 24px #36492e24}.topic-category-card:hover,.topic-category-card:focus-visible{border-color:#3d5d3159}.topic-category-card h2{margin:0;color:var(--accent-strong);font-size:clamp(1.02rem,2vw,1.22rem);line-height:1.3}.topic-page-shell{min-height:100dvh;padding:6px 8px calc(6px + env(safe-area-inset-bottom));display:flex;flex-direction:column;gap:4px}.topic-topbar{display:flex;align-items:center;gap:8px}.topic-topbar h1{flex:1;min-width:0;margin:0;font-size:clamp(1.08rem,2.4vw,1.48rem);line-height:1.15;text-align:center;color:var(--accent-strong)}.flashcard-panel{display:flex;flex:1;min-height:0;flex-direction:column;gap:4px;padding:6px 6px 4px}.status-row{display:flex;justify-content:flex-start;gap:8px;align-items:center;margin:0}.progress-text{margin:0;color:var(--text-muted);font-weight:700;font-size:.86rem;line-height:1;padding:5px 9px;border-radius:999px;background:#567a471a}.card-shell{width:100%;flex:0 0 auto;min-height:350px;height:clamp(350px,62dvh,590px);border:0;background:transparent;padding:0;cursor:pointer;perspective:1600px}.card-inner{position:relative;height:100%;transform-style:preserve-3d;transition:transform .7s ease}.card-inner.is-flipped{transform:rotateY(180deg)}.card-face{position:absolute;top:0;right:0;bottom:0;left:0;border-radius:20px;border:1px solid var(--border);padding:12px 14px 10px;backface-visibility:hidden;display:flex;flex-direction:column;gap:10px;overflow:auto;box-shadow:inset 0 1px #fff6}.card-front{background:var(--card-front)}.card-back{background:var(--card-back);transform:rotateY(180deg)}.face-chip{position:absolute;top:6px;right:6px;padding:3px 6px;border-radius:999px;background:#567a471f;color:var(--accent-strong);font-weight:700;font-size:.64rem;line-height:1}.back-chip{background:#567a472e}.topic-chip{align-self:flex-start}.card-content{display:flex;flex-direction:column;gap:8px;text-align:center;align-items:center;flex:1;justify-content:center;padding-top:10px}.card-line{margin:0;width:100%;font-size:clamp(1.36rem,3vw,1.88rem);line-height:1.3;font-weight:600}.card-line.main-title{font-weight:800;color:var(--accent-strong);font-size:clamp(1.52rem,3.5vw,2.1rem)}.blank-emphasis{display:inline-block;min-width:5.4ch;padding:.06em .34em .12em;margin:0 .06em;border-bottom:3px solid var(--blank-border);border-radius:10px;background:var(--blank-bg);letter-spacing:.1em;font-weight:900;color:#7b5200}.answer-highlight{display:inline;padding:.08em .32em;border-radius:10px;background:var(--answer-bg);color:#214b17;box-decoration-break:clone;-webkit-box-decoration-break:clone}.translation-box,.media-box{border-radius:12px;padding:6px 8px;background:#567a4714;text-align:center}.translation-box{font-size:.92rem;line-height:1.32}.translation-box p{margin:0}.media-box{color:var(--text-muted)}.controls{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:6px;margin-top:-10px;position:sticky;bottom:8px;padding-top:2px;background:linear-gradient(180deg,#f7f7f200,#f7f7f2e6 22%,#f7f7f2fb)}.nav-button{min-width:0;border:1px solid rgba(86,122,71,.2);border-radius:999px;padding:9px 12px;background:#fff;color:var(--accent-strong);font-weight:700;cursor:pointer;text-decoration:none;transition:transform .2s ease,box-shadow .2s ease,background .2s ease}.nav-button.primary{background:var(--accent-strong);color:#fff}.nav-button.ghost{background:#ffffffb8}.nav-button.compact-back{padding:7px 11px;font-size:.86rem;white-space:nowrap}.card-shell:focus-visible .card-face{border-color:#3d5d3173}@media(max-width:640px){.page-shell{padding:24px 14px 40px}.app-panel,.topic-category-card{padding:16px;border-radius:20px}.home-page-shell{padding:20px 12px 32px}.topic-page-shell{padding:4px 4px calc(6px + env(safe-area-inset-bottom));gap:3px}.home-hero{margin-bottom:12px}.topics-panel{padding:12px}.flashcard-panel{gap:3px;padding:4px 4px 2px;border-radius:12px}.topic-topbar{gap:5px}.topic-topbar h1{font-size:1rem}.progress-text{font-size:.72rem;padding:3px 6px}.card-shell{min-height:360px;height:clamp(360px,64dvh,620px)}.card-face{padding:10px 10px 9px;gap:8px}.face-chip{top:5px;right:5px;font-size:.58rem}.card-content{gap:6px;padding-top:8px}.card-line{font-size:clamp(1.34rem,5.1vw,1.58rem);line-height:1.24}.card-line.main-title{font-size:clamp(1.48rem,5.8vw,1.8rem)}.blank-emphasis{min-width:4.9ch;border-bottom-width:3px}.translation-box,.media-box{padding:5px 7px;border-radius:10px}.translation-box{font-size:.86rem;line-height:1.28}.nav-button{padding:8px 10px;font-size:.9rem}.nav-button.compact-back{padding:5px 8px;font-size:.74rem}.controls{gap:5px;margin-top:-12px;padding-top:1px;bottom:10px}.topic-category-card{min-height:64px;padding:12px 10px}.topics-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.topic-category-card h2{font-size:.98rem}}