*{box-sizing:border-box;-webkit-text-size-adjust:100%}
html,body{margin:0;padding:0}
body{background:#fff;color:#0D337B;font-family:Montserrat,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif}
html[lang=ja] body,html[lang=ja] .fig svg text{font-family:Montserrat,"Hiragino Sans","Hiragino Kaku Gothic ProN","Noto Sans JP","Yu Gothic",sans-serif}
html[lang=zh-Hans] body,html[lang=zh-Hans] .fig svg text{font-family:Montserrat,"PingFang SC","Noto Sans SC","Microsoft YaHei",sans-serif}
html[lang=th] body,html[lang=th] .fig svg text{font-family:Montserrat,"Noto Sans Thai","Thonburi","Leelawadee UI",sans-serif}
.hidden{display:none}
#gate{position:fixed;inset:0;background:linear-gradient(150deg,#0D337B,#124a8f 60%,#3CB8D6);display:flex;align-items:center;justify-content:center;z-index:999;padding:24px}
#gate .box{background:#fff;border-radius:14px;padding:32px 28px;max-width:380px;width:100%;box-shadow:0 20px 50px rgba(0,0,0,.3);text-align:center}
#gate h1{font-size:19px;margin:0 0 6px;color:#0D337B}
#gate p{font-size:14px;color:#667;margin:0 0 20px}
#gate input{width:100%;padding:14px;font-size:17px;border:2px solid #e3e9ee;border-radius:9px;text-align:center;margin-bottom:12px}
#gate input:focus{outline:none;border-color:#3CB8D6}
#gate button{width:100%;padding:14px;font-size:17px;font-weight:600;background:#0D337B;color:#fff;border:none;border-radius:9px;cursor:pointer}
#gate .err{color:#c0392b;font-size:14px;height:18px;margin-top:10px}
header{background:linear-gradient(120deg,#0D337B,#124a8f 70%,#3CB8D6);color:#fff;padding:22px 20px 18px;position:sticky;top:0;z-index:50;box-shadow:0 2px 12px rgba(0,0,0,.15)}
header .title{font-size:20px;font-weight:700;margin:0 0 2px}
header .sub{font-size:13px;opacity:.85}
header .title,header .sub{padding-right:92px}
.langtoggle{display:flex;gap:8px;margin-top:14px;flex-wrap:wrap}
.langtoggle a,.langtoggle span{flex:1;min-width:70px;text-align:center;padding:10px;font-size:15px;font-weight:600;border-radius:8px;background:rgba(255,255,255,.18);color:#fff;text-decoration:none}
.langtoggle a.active{background:#fff;color:#0D337B}
.langtoggle span{opacity:.45}
.menubtn{position:absolute;top:18px;right:16px;background:rgba(255,255,255,.18);color:#fff;border:1px solid rgba(255,255,255,.45);border-radius:8px;padding:7px 12px;font-size:14px;font-weight:700;cursor:pointer;font-family:inherit}
.mshade{position:fixed;inset:0;background:rgba(0,0,0,.35);z-index:200;display:none}
.mpanel{position:fixed;top:0;right:0;bottom:0;width:min(82vw,300px);background:#fff;z-index:201;transform:translateX(100%);transition:transform .2s ease;box-shadow:-4px 0 18px rgba(0,0,0,.2);padding:18px 0;overflow-y:auto}
body.mopen .mshade{display:block} body.mopen .mpanel{transform:none}
.mpanel .mclose{display:block;margin:0 16px 10px auto;background:none;border:0;font-size:15px;font-weight:700;color:#0D337B;cursor:pointer;font-family:inherit}
.mpanel a{display:block;padding:14px 22px;font-size:16px;font-weight:600;color:#0D337B;text-decoration:none;border-bottom:1px solid #e6ebf2}
.mpanel a.cur{background:#eaf3fb;border-left:4px solid #3CB8D6;padding-left:18px}
footer{text-align:center;padding:20px;font-size:13px;color:#889}
section{scroll-margin-top:190px}
.crumb{margin:0 0 14px;font-size:14px} .crumb a{color:#377F75;font-weight:700;text-decoration:none}
.mods{display:grid;gap:12px;max-width:820px;padding:0;list-style:none}
.mods li{border:1px solid #e3e8f0;border-radius:10px;padding:16px 18px;display:flex;gap:14px;align-items:center;flex-wrap:wrap}
.mods .num{width:38px;height:38px;border-radius:50%;background:#0D337B;color:#fff;display:flex;align-items:center;justify-content:center;font-weight:700;flex:none}
.mods .t{flex:1;min-width:0} .mods .t b{display:block;font-size:17px} .mods .t span{font-size:14px;color:#556}
.mods a.go{background:#0D337B;color:#fff;text-decoration:none;font-weight:700;border-radius:8px;padding:9px 16px}
.mods .soon{color:#9aa3b2;font-weight:600;font-size:14px}
.mods li.off{opacity:.55}
.pill{display:inline-block;font-size:12px;font-weight:700;color:#C59E4F;margin-top:4px}
header .sub{color:#fff;margin:0}
@media(max-width:560px){.mods li{align-items:flex-start}.mods a.go{width:100%;text-align:center}}
.qsoon{background:#f3f6fb;border-left:4px solid #377F75;padding:12px 16px;margin:24px 0 0;max-width:820px;line-height:1.5}

html.i18n-wait #site{visibility:hidden}
.langtoggle button{flex:1;min-width:70px;text-align:center;padding:10px;font-size:15px;font-weight:600;border-radius:8px;background:rgba(255,255,255,.18);color:#fff;border:0;cursor:pointer;font-family:inherit}
.langtoggle button.active{background:#fff;color:#0D337B}
.langtoggle button:disabled{opacity:.45;cursor:default}



main{max-width:1100px;margin:0 auto;padding:24px 16px 80px}
h1{font-size:28px;margin:0 0 4px} .sub{color:#556;margin:0 0 28px}
section{border-top:1px solid #e3e8f0;padding:28px 0}
h2{font-size:21px;margin:0 0 8px} h3{font-size:16px;margin:22px 0 6px;color:#377F75} p{line-height:1.55;margin:0 0 14px;max-width:820px}
.fig svg{width:100%;height:auto;display:block} .fig svg text{font-family:Montserrat,system-ui,sans-serif}
.trio{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}
.ift{margin:18px 0 10px;display:grid;gap:8px} .row{display:grid;grid-template-columns:1fr 1fr;gap:8px}
.if,.then{padding:10px 14px;border-radius:8px;line-height:1.45} .if{background:#f3f6fb} .then{background:#e8f4f2}
.if b{color:#C59E4F} .then b{color:#377F75}
.rem{background:#0D337B;color:#fff;padding:12px 16px;border-radius:8px;font-size:17px}
table{border-collapse:collapse;width:100%;max-width:900px} td{border-bottom:1px solid #e3e8f0;padding:10px 12px;vertical-align:top;line-height:1.45} td:first-child{width:42%;font-weight:600} th{text-align:left;padding:10px 12px;border-bottom:2px solid #0D337B} .salt td:first-child{width:40%}
.words td:first-child{width:24%}
@media(max-width:700px){.row{grid-template-columns:1fr}}
.rule{background:#eaf6fa;border-left:6px solid #3CB8D6;padding:14px 16px;margin:18px 0;line-height:1.55;font-size:17px} .rule b{color:#0D337B} .rule.crit{background:#fdecea;border-left-color:#c0392b} .rule.crit b{color:#c0392b}
.note{background:#f3f6fb;border-left:4px solid #377F75;padding:10px 14px}
.flag{background:#fdf3e1;border-left:4px solid #C59E4F;padding:10px 14px;font-weight:600}
.key{display:flex;flex-wrap:wrap;gap:18px;font-size:14px;margin-bottom:8px} .key span::before{content:"";display:inline-block;width:14px;height:14px;margin-right:6px;vertical-align:-2px;background:var(--c)}
@media(max-width:700px){.trio{grid-template-columns:1fr}}

:root{color-scheme:light} body{background:#fff} main{padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
h1,h2{text-wrap:balance}
.eyebrow{font-size:13px;letter-spacing:.08em;text-transform:uppercase;color:#377F75;font-weight:700;margin:0 0 6px}
.toc{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 8px;padding:0;list-style:none} .toc a{display:block;padding:6px 10px;border:1px solid #e3e8f0;border-radius:6px;color:#0D337B;text-decoration:none;font-size:13px;font-weight:600} .toc a:hover{border-color:#3CB8D6}
.list{max-width:820px;padding-left:20px;line-height:1.55} .list li{margin:0 0 8px}
.carry td:first-child{width:38%} .fig{overflow-x:auto}
.think{margin:10px 0;border:2px solid #C59E4F;border-radius:8px;padding:12px 16px;background:#fdf8ef} .think summary{cursor:pointer;font-weight:600;line-height:1.5} .think .tag{display:inline-block;background:#C59E4F;color:#fff;font-size:12px;letter-spacing:.06em;text-transform:uppercase;padding:2px 8px;border-radius:4px;margin-right:8px} .think p{margin:10px 0 0;color:#377F75;font-weight:600}
.src ol{line-height:1.7;font-size:14px} .src a{color:#0D337B}
/* quiz */
#qz{max-width:860px} .qhead{display:flex;flex-wrap:wrap;gap:12px;align-items:center;justify-content:space-between;margin-bottom:14px}
.btn{font:inherit;font-weight:700;border:2px solid #0D337B;background:#0D337B;color:#fff;border-radius:8px;padding:10px 18px;cursor:pointer} .btn.alt{background:#fff;color:#0D337B} .btn:disabled{opacity:.4;cursor:default} .btn:focus-visible,.opt:focus-visible{outline:3px solid #3CB8D6;outline-offset:2px}
.qcard{border:1px solid #e3e8f0;border-radius:10px;padding:18px} .qmeta{font-size:12px;letter-spacing:.06em;text-transform:uppercase;color:#377F75;font-weight:700;margin-bottom:6px}
.qtext{font-size:17px;font-weight:600;line-height:1.5;margin:0 0 14px}
.opt{display:block;width:100%;text-align:left;font:inherit;line-height:1.45;background:#f3f6fb;border:2px solid transparent;border-radius:8px;padding:12px 14px;margin:0 0 8px;cursor:pointer;color:#0D337B} .opt:hover:not(:disabled){border-color:#3CB8D6}
.opt.right{background:#e8f4f2;border-color:#377F75} .opt.wrong{background:#fdecea;border-color:#c0392b} .opt:disabled{cursor:default}
.exp{margin-top:12px;padding:12px 14px;border-radius:8px;background:#f3f6fb;line-height:1.55} .exp b.ok{color:#377F75} .exp b.no{color:#c0392b}
.bar{height:8px;background:#e3e8f0;border-radius:4px;overflow:hidden;margin:6px 0 0} .bar i{display:block;height:100%;background:#377F75}
.res{font-size:22px;font-weight:700;margin:0 0 6px} .pass{color:#377F75} .fail{color:#c0392b}
.bd td{font-variant-numeric:tabular-nums} .bank li{margin:0 0 14px;line-height:1.5} .bank .ans{color:#377F75;font-weight:600}

/* Textbook layout (2026-10-25): callout boxes only for real rules (.rule, .rule.crit). Everything else is plain text. */
.ift{margin:20px 0 14px;display:block;max-width:900px}
.ift table{width:100%;border-collapse:collapse}
.ift th{font-size:13px;letter-spacing:.06em;text-transform:uppercase;color:#556;border-bottom:2px solid #0D337B;padding:8px 10px;text-align:left}
.ift td{border-bottom:1px solid #e3e8f0;padding:9px 10px;vertical-align:top;line-height:1.45;font-weight:500}
.ift td:first-child{width:46%;font-weight:600}
.ift .row{display:grid;grid-template-columns:1fr 1fr;gap:0;border-bottom:1px solid #e3e8f0}
.ift .if,.ift .then{background:none;border-radius:0;padding:9px 10px}
.ift .if b,.ift .then b{display:none}
.cyu{margin:18px 0 8px;max-width:900px}
.cyu h4{font-size:13px;letter-spacing:.06em;text-transform:uppercase;color:#556;margin:0 0 6px}
.think{margin:0;border:0;border-bottom:1px solid #e3e8f0;border-radius:0;padding:9px 0;background:none}
.think summary{cursor:pointer;font-weight:600;line-height:1.5}
.think .tag{display:none}
.think p{margin:8px 0 2px 18px;color:#377F75;font-weight:500}
.rem{background:none;color:#0D337B;padding:10px 0 0;border-radius:0;font-size:16px;border-top:2px solid #0D337B;max-width:900px;margin-top:14px}
.rem b{text-transform:uppercase;font-size:13px;letter-spacing:.06em;margin-right:6px}
.loopstrip{display:flex;flex-wrap:wrap;gap:6px;list-style:none;padding:0;margin:4px 0 16px;counter-reset:none}
.loopstrip li{border:2px solid #c9d3e3;color:#8a94a6;border-radius:999px;padding:5px 12px;font-size:13px;font-weight:700;white-space:nowrap}
.loopstrip li.on{background:#0D337B;border-color:#0D337B;color:#fff}
@media(max-width:700px){.ift td{font-size:15px;padding:8px 6px}.ift .row{grid-template-columns:1fr 1fr}}
.fig svg.mfig{max-width:560px;margin:10px 0 16px}
@media(max-width:600px){table.carry{display:block;overflow-x:auto;-webkit-overflow-scrolling:touch}}