:root{--bg:#f3f6f4;--paper:#fff;--ink:#20302b;--muted:#66736f;--line:#d7e0dc;--accent:#4e756a;--accent2:#7a6658;--soft:#e8f0ed;--warn:#fff5df;--danger:#fae9e6;--shadow:0 10px 30px rgba(34,54,48,.08)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-family:"Noto Sans TC","PingFang TC","Microsoft JhengHei",sans-serif;line-height:1.75}.top{position:sticky;top:0;z-index:30;background:rgba(243,246,244,.96);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}.topin{max-width:1160px;margin:auto;padding:.72rem 1rem;display:flex;justify-content:space-between;gap:1rem}.brand,.back{font-weight:800;text-decoration:none}.brand{color:var(--ink)}.back{color:var(--accent)}.hero{max-width:1160px;margin:auto;padding:3.4rem 1rem 1.8rem}.eyebrow{color:var(--accent);font-weight:900;letter-spacing:.08em}.hero h1{font-size:clamp(2.15rem,5vw,4rem);line-height:1.12;margin:.35rem 0 .8rem}.lead{max-width:850px;color:var(--muted);font-size:1.08rem}.toc{display:flex;gap:.5rem;flex-wrap:wrap;margin-top:1rem}.toc a{background:var(--soft);color:var(--accent);text-decoration:none;padding:.4rem .72rem;border-radius:999px;font-weight:800}main{max-width:1160px;margin:auto;padding:0 1rem 4rem}.sec{background:var(--paper);border:1px solid var(--line);border-radius:22px;padding:clamp(1.1rem,3vw,2rem);margin:1rem 0;box-shadow:var(--shadow)}.sec h2{font-size:clamp(1.45rem,3vw,2rem);margin:.12rem 0 .7rem}.sec h3{margin:1.25rem 0 .4rem}.tag{display:inline-block;padding:.2rem .66rem;border-radius:999px;background:var(--soft);color:var(--accent);font-weight:900;font-size:.84rem}.priority{float:right;font-size:.8rem;font-weight:900;padding:.2rem .55rem;border-radius:8px;background:#eef1ef;color:#485651}.grid2,.grid3,.grid4{display:grid;gap:1rem}.grid2{grid-template-columns:repeat(2,minmax(0,1fr))}.grid3{grid-template-columns:repeat(3,minmax(0,1fr))}.grid4{grid-template-columns:repeat(4,minmax(0,1fr))}.box{border:1px solid var(--line);border-radius:16px;padding:1rem;background:#fcfdfc}.box h3{margin:.1rem 0 .35rem}.key{border-left:5px solid var(--accent);background:var(--soft);padding:1rem 1.1rem;border-radius:12px;margin:1rem 0}.warn{border-left-color:#b67b2f;background:var(--warn)}.danger{border-left-color:#b85f55;background:var(--danger)}.formula{font-size:clamp(1.12rem,3vw,1.55rem);font-weight:900;text-align:center;padding:1rem;border:1px dashed var(--accent);border-radius:14px;background:#fbfdfc}.tablewrap{overflow:auto}.tbl{width:100%;border-collapse:collapse;min-width:650px}.tbl th,.tbl td{border:1px solid var(--line);padding:.72rem;vertical-align:top}.tbl th{background:var(--soft);text-align:left}.steps{counter-reset:s}.steps li{list-style:none;margin:.68rem 0;padding-left:2.45rem;position:relative}.steps li:before{counter-increment:s;content:counter(s);position:absolute;left:0;top:.03rem;width:1.72rem;height:1.72rem;border-radius:50%;display:grid;place-items:center;background:var(--accent);color:#fff;font-weight:900}.quiz{border:1px solid var(--line);border-radius:16px;padding:1rem;margin:1rem 0;background:#fbfcfb}.quiz button,.choice button{margin:.3rem .35rem .3rem 0;padding:.65rem .9rem;border:1px solid var(--line);background:#fff;border-radius:10px;cursor:pointer;font:inherit}.feedback{font-weight:900;min-height:1.5rem}.video{display:flex;justify-content:space-between;gap:1rem;align-items:center;border:1px solid var(--line);padding:1rem;border-radius:14px;margin:.7rem 0}.video a,.btn{display:inline-block;text-decoration:none;color:#fff;background:var(--accent);padding:.65rem .92rem;border-radius:10px;font-weight:900}.video small{display:block;color:var(--muted)}.download{background:var(--accent2)}details{border:1px solid var(--line);border-radius:14px;padding:.8rem 1rem;margin:.7rem 0}summary{cursor:pointer;font-weight:900}.footer{padding:2rem 1rem;text-align:center;color:var(--muted)}.calc{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:.72rem;align-items:end}.calc label{font-weight:800}.calc input,.calc select{width:100%;padding:.65rem;border:1px solid var(--line);border-radius:9px;font:inherit}.calc button{padding:.75rem;border:0;border-radius:9px;background:var(--accent);color:#fff;font-weight:900;cursor:pointer}.result{font-weight:900;font-size:1.08rem}.mini-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(160px,1fr));gap:.7rem}.pill{padding:.75rem;border-radius:12px;background:var(--soft);font-weight:800}.navgrid{display:grid;grid-template-columns:repeat(auto-fit,minmax(225px,1fr));gap:1rem}.navcard{display:block;padding:1.1rem;background:#fff;border:1px solid var(--line);border-radius:18px;text-decoration:none;color:var(--ink);box-shadow:var(--shadow)}.navcard b{display:block}.navcard small{color:var(--muted)}.diagram{display:flex;justify-content:center;align-items:center;gap:.5rem;flex-wrap:wrap;margin:1rem 0}.state{padding:.9rem 1.1rem;border-radius:14px;background:var(--soft);font-weight:900}.arrow{font-size:1.4rem;color:var(--accent)}.meter{height:12px;background:#e8ecea;border-radius:999px;overflow:hidden}.meter span{display:block;height:100%;background:var(--accent)}.checklist label{display:block;padding:.48rem 0;border-bottom:1px dashed var(--line)}.tiny{font-size:.9rem;color:var(--muted)}@media(max-width:780px){.grid2,.grid3,.grid4{grid-template-columns:1fr}.hero{padding-top:2.2rem}.video{align-items:flex-start;flex-direction:column}.sec{border-radius:16px}.tbl{font-size:.92rem}.priority{float:none;display:inline-block;margin-left:.4rem}}

/* Single-page lesson layout */
.chapter-nav{position:sticky;top:49px;z-index:24;background:rgba(255,255,255,.96);border-top:1px solid var(--line);border-bottom:1px solid var(--line);backdrop-filter:blur(10px)}
.chapter-nav-inner{max-width:1160px;margin:auto;padding:.62rem 1rem;display:flex;gap:.48rem;overflow-x:auto;scrollbar-width:thin}
.chapter-nav a{white-space:nowrap;text-decoration:none;color:var(--accent);font-weight:850;padding:.38rem .68rem;border-radius:999px;background:var(--soft)}
.unit{scroll-margin-top:108px;margin:2.3rem 0 3.6rem}.unit-heading{padding:0 .2rem .55rem;border-bottom:2px solid var(--accent);margin-bottom:.9rem}.unit-heading h2{font-size:clamp(1.75rem,4vw,2.7rem);margin:.1rem 0}.unit-kicker{margin:0;color:var(--muted);font-size:.86rem;font-weight:800;letter-spacing:.04em}.unit>.sec{box-shadow:none;border-radius:15px;margin:.68rem 0;padding:clamp(1rem,2.4vw,1.6rem)}.unit>.sec+.sec{border-top-color:#e2e8e5}.intro{margin-top:.2rem}.to-top{position:fixed;right:1rem;bottom:1rem;width:2.8rem;height:2.8rem;border-radius:50%;display:grid;place-items:center;text-decoration:none;background:var(--accent);color:#fff;font-size:1.4rem;font-weight:900;box-shadow:var(--shadow);z-index:20}
@media(max-width:780px){.chapter-nav{top:48px}.chapter-nav-inner{padding:.5rem .7rem}.unit{scroll-margin-top:100px;margin:1.7rem 0 2.7rem}.unit>.sec{padding:1rem}.hero h1{font-size:2.25rem}.topin{font-size:.9rem}.back{white-space:nowrap}}

/* v5 實驗模組 */
.experiment{margin:1.5rem 0;padding:1.25rem;border:1px solid #b8c8c2;border-radius:18px;background:#f7faf8;box-shadow:0 8px 24px rgba(30,55,48,.06)}
.experiment h3{margin:.15rem 0 .45rem;font-size:1.35rem}.experiment .exp-title{display:flex;gap:.75rem;align-items:flex-start;justify-content:space-between;flex-wrap:wrap}.exp-badge{display:inline-block;padding:.25rem .65rem;border-radius:999px;background:#dcebe5;font-size:.82rem;font-weight:700}.exp-grid{display:grid;grid-template-columns:minmax(260px,.9fr) minmax(300px,1.1fr);gap:1rem;margin-top:1rem}.exp-panel{background:#fff;border:1px solid #d8e2de;border-radius:14px;padding:1rem}.exp-panel h4{margin:0 0 .45rem;font-size:1.05rem}.apparatus{width:100%;min-height:220px;background:#eef4f1;border-radius:12px;border:1px solid #d4e0db;display:flex;align-items:center;justify-content:center;overflow:hidden}.apparatus svg{width:100%;height:auto;display:block}.exp-steps{counter-reset:expstep;list-style:none;padding:0;margin:.3rem 0}.exp-steps li{counter-increment:expstep;position:relative;padding:.35rem .25rem .35rem 2.35rem;border-bottom:1px dashed #dce4e1}.exp-steps li:before{content:counter(expstep);position:absolute;left:.25rem;top:.28rem;width:1.45rem;height:1.45rem;border-radius:50%;display:grid;place-items:center;background:#385f53;color:white;font-weight:700;font-size:.82rem}.exp-result{border-left:4px solid #4a7b6a;background:#edf5f1;padding:.8rem 1rem;border-radius:8px;margin:.65rem 0}.exp-question{border-left:4px solid #b9873d;background:#fbf4e8;padding:.8rem 1rem;border-radius:8px;margin:.65rem 0}.exp-safety{border-left:4px solid #a85252;background:#faeeee;padding:.8rem 1rem;border-radius:8px;margin:.65rem 0}.exp-tags{display:flex;gap:.4rem;flex-wrap:wrap;margin:.6rem 0}.exp-tags span{padding:.18rem .5rem;border:1px solid #c7d6d0;border-radius:999px;font-size:.78rem;background:white}.experiment details{margin-top:.75rem;border-top:1px solid #d7e2dd;padding-top:.7rem}.experiment summary{cursor:pointer;font-weight:700}.compare-strip{display:grid;grid-template-columns:repeat(3,1fr);gap:.5rem;margin:.7rem 0}.compare-strip>div{padding:.7rem;border-radius:10px;background:#eef4f1;text-align:center}.mini-observe{display:grid;grid-template-columns:repeat(2,1fr);gap:.65rem}.mini-observe div{background:white;border:1px solid #d8e2de;border-radius:10px;padding:.7rem}.exp-video-row{display:flex;gap:.55rem;flex-wrap:wrap;margin-top:.65rem}.exp-video-row a{display:inline-block;padding:.45rem .75rem;border-radius:10px;background:#355d51;color:white;text-decoration:none;font-weight:700}.experiment-table{width:100%;border-collapse:collapse}.experiment-table th,.experiment-table td{border:1px solid #d4dfda;padding:.45rem;text-align:center}.experiment-table th{background:#e8f0ec}@media(max-width:760px){.exp-grid{grid-template-columns:1fr}.apparatus{min-height:170px}.compare-strip{grid-template-columns:1fr}.mini-observe{grid-template-columns:1fr}}


/* 題目導向學習區 */
.question-zone{background:linear-gradient(180deg,#f8faf8,#eef4f1);border-left:5px solid #6f8d82}
.qz-head{max-width:820px;margin-bottom:1.2rem}.qz-head h2{margin:.45rem 0}.qz-head p{color:#52645e}
.source-quiz{display:grid;gap:1rem}.source-q{display:grid;grid-template-columns:52px 1fr;gap:1rem;background:#fff;border:1px solid #d7e1dc;border-radius:14px;padding:1.05rem;box-shadow:0 4px 14px rgba(41,62,54,.05)}
.source-q-no{width:44px;height:44px;border-radius:50%;display:grid;place-items:center;background:#e5eee9;color:#3e5b51;font-weight:800}.source-q h3{font-size:1.02rem;line-height:1.55;margin:.15rem 0 .9rem}
.source-options{display:grid;grid-template-columns:1fr 1fr;gap:.6rem}.source-options button{display:flex;align-items:flex-start;gap:.55rem;text-align:left;border:1px solid #cfdad5;background:#fafcfb;border-radius:10px;padding:.7rem .8rem;line-height:1.45;cursor:pointer;color:#263832}.source-options button span{display:grid;place-items:center;min-width:24px;height:24px;border-radius:50%;background:#e7eeeb;font-weight:800}.source-options button:hover{border-color:#78988c;background:#f2f7f4}.source-options button.correct{background:#e2f3e9;border-color:#52906c}.source-options button.wrong{background:#f8e5e2;border-color:#b86c61}.source-answer{margin-top:.8rem;padding:.75rem .9rem;border-radius:9px;background:#f0f5f2}.source-answer b{color:#345c4d}.source-answer p{margin:.35rem 0 0;color:#4b5f57}
.question-map{background:#263f37;color:#f4f8f6}.question-map h2,.question-map .lead-small{color:#fff}.qmap-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.75rem;margin-top:1rem}.qmap-grid div{display:flex;flex-direction:column;gap:.25rem;padding:1rem;border:1px solid rgba(255,255,255,.18);border-radius:12px;background:rgba(255,255,255,.06)}.qmap-grid b{font-size:1.05rem}.qmap-grid span{color:#d9e5e0;line-height:1.5}.lead-small{opacity:.88}
@media(max-width:700px){.source-q{grid-template-columns:1fr}.source-q-no{width:36px;height:36px}.source-options{grid-template-columns:1fr}.qmap-grid{grid-template-columns:1fr}}

/* v7 resource-rich additions */
.video-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px;margin-top:22px}.video-grid.single{grid-template-columns:minmax(0,760px)}.video-card{background:var(--card,#fff);border:1px solid rgba(64,86,77,.18);border-radius:18px;padding:14px;box-shadow:0 8px 26px rgba(42,63,55,.08)}.video-card h3{margin:.75rem 0 .25rem}.video-card p{margin:.25rem 0;color:#52645d}.ratio{position:relative;width:100%;aspect-ratio:16/9;border-radius:12px;overflow:hidden;background:#111}.ratio iframe{position:absolute;inset:0;width:100%;height:100%;border:0}.prefix-ladder{display:grid;grid-template-columns:repeat(11,minmax(62px,1fr));gap:8px;overflow-x:auto;padding:10px 0}.prefix-ladder span{min-width:62px;text-align:center;padding:12px 6px;border-radius:12px;background:#eef5f1;border:1px solid #cfddd7;font-weight:800}.prefix-ladder small{font-weight:500}.formula-grid,.method-flow{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin:18px 0}.formula-grid>div,.method-flow>div{display:flex;justify-content:space-between;gap:18px;padding:15px 18px;border:1px solid rgba(64,86,77,.18);border-radius:14px;background:#f7faf8}.method-flow>div span{max-width:68%;text-align:right}.volume-method-svg svg{width:100%;height:auto}.embedded-videos .video-card{align-self:start}@media(max-width:760px){.video-grid,.formula-grid,.method-flow{grid-template-columns:1fr}.method-flow>div{display:block}.method-flow>div span{display:block;max-width:none;text-align:left;margin-top:5px}.prefix-ladder{grid-template-columns:repeat(11,72px)}}

/* Complete YouTube library */
.full-video-library{scroll-margin-top:88px}.video-library-toolbar{display:flex;gap:.75rem;align-items:center;flex-wrap:wrap;margin:1rem 0 1.25rem;padding:1rem;border:1px solid var(--line,#d8e2de);border-radius:14px;background:#f7faf8}.video-library-toolbar label{font-weight:700}.video-library-toolbar input{flex:1;min-width:220px;padding:.72rem .9rem;border:1px solid #b9c9c2;border-radius:10px;font:inherit}.video-library-toolbar button{border:0;border-radius:10px;padding:.72rem 1rem;background:#3f6559;color:#fff;font-weight:700;cursor:pointer}.video-count{font-size:.92rem;color:#567067}.video-group{margin:1rem 0;border:1px solid #d6e0dc;border-radius:14px;overflow:hidden;background:#fff}.video-group>summary{cursor:pointer;display:flex;justify-content:space-between;align-items:center;padding:1rem 1.1rem;font-weight:800;background:#eef4f1}.video-group>summary span{font-weight:600;color:#667d75}.yt-library-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:1rem;padding:1rem}.yt-link-card{border:1px solid #dbe4e0;border-radius:12px;overflow:hidden;background:#fff;box-shadow:0 4px 14px rgba(43,66,58,.06)}.yt-thumb{position:relative;display:block;aspect-ratio:16/9;background:#dfe8e4;overflow:hidden}.yt-thumb img{width:100%;height:100%;object-fit:cover;display:block}.yt-play{position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);width:48px;height:48px;border-radius:50%;display:grid;place-items:center;background:rgba(173,32,24,.92);color:#fff;font-size:1.15rem;padding-left:3px}.yt-duration{position:absolute;right:7px;bottom:7px;padding:.18rem .38rem;border-radius:4px;background:rgba(0,0,0,.78);color:#fff;font-size:.78rem}.yt-card-body{padding:.82rem .9rem 1rem}.yt-card-body h4{margin:0 0 .45rem;font-size:1rem;line-height:1.4}.yt-card-body p{margin:0 0 .65rem;color:#6d7d77;font-size:.82rem}.yt-card-body a{font-weight:700;color:#315f51;text-decoration:none}.yt-link-card[hidden]{display:none!important}@media(max-width:620px){.yt-library-grid{grid-template-columns:1fr}.video-library-toolbar{align-items:stretch}.video-library-toolbar input,.video-library-toolbar button{width:100%}}