:root{
  --bg:#f7f6f2;--surface:#ffffff;--ink:#1d2321;--muted:#5b6461;--line:#dfe2dd;
  --brand:#0b6e79;--brand-ink:#ffffff;--brand-soft:#e3f4f5;--accent:#c2410c;
  --warn-bg:#fff7e6;--warn-line:#f2c46b;
  --radius:12px;--max:1080px;
  --font:"Hiragino Sans","Noto Sans JP","Yu Gothic UI",Meiryo,system-ui,-apple-system,"Segoe UI",Roboto,Arial,sans-serif;
}
@media (prefers-color-scheme:dark){
  :root{--bg:#121614;--surface:#1a201d;--ink:#e8ece9;--muted:#a3ada8;--line:#2c3430;
    --brand:#4fc3cf;--brand-ink:#08130e;--brand-soft:#14302f;--accent:#fb923c;
    --warn-bg:#2a2414;--warn-line:#7a5d1e;}
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.65 var(--font)}
a{color:var(--brand)}
img{max-width:100%;height:auto}
.wrap{max-width:var(--max);margin:0 auto;padding:0 16px}

/* header */
.site-header{background:var(--surface);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:58px}
.logo{font-weight:800;color:var(--ink);text-decoration:none;font-size:1.05rem;letter-spacing:-.01em}
.logo span{color:var(--brand)}
.nav{display:flex;gap:4px;flex-wrap:wrap}
.nav a{color:var(--muted);text-decoration:none;padding:6px 10px;border-radius:8px;font-size:.92rem}
.nav a:hover,.nav a[aria-current="page"]{background:var(--brand-soft);color:var(--brand)}
.menu-btn{display:none;background:none;border:1px solid var(--line);border-radius:8px;padding:6px 10px;color:var(--ink);font:inherit}
@media (max-width:820px){
  .menu-btn{display:block}
  .nav{display:none;position:absolute;top:58px;left:0;right:0;background:var(--surface);border-bottom:1px solid var(--line);flex-direction:column;padding:8px 16px 14px}
  .nav.open{display:flex}
}

/* layout */
main{padding:28px 0 48px}
.breadcrumb{font-size:.85rem;color:var(--muted);margin-bottom:10px}
.breadcrumb a{color:var(--muted)}
h1{font-size:clamp(1.7rem,4vw,2.4rem);line-height:1.2;margin:0 0 10px;letter-spacing:-.02em}
h2{font-size:1.45rem;line-height:1.3;margin:2.2em 0 .6em;letter-spacing:-.01em}
h3{font-size:1.12rem;margin:1.6em 0 .4em}
.lead{font-size:1.08rem;color:var(--muted);max-width:68ch;margin:0 0 20px}
.updated{font-size:.85rem;color:var(--muted)}
.content{max-width:760px}
.content p,.content li{max-width:70ch}
.grid-2{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:32px;align-items:start}
@media (max-width:960px){.grid-2{grid-template-columns:minmax(0,1fr)}}

/* calculator */
.calc{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:20px;box-shadow:0 1px 2px rgba(0,0,0,.04)}
.calc h2{margin-top:0;font-size:1.2rem}
.fields{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}
@media (max-width:560px){.fields{grid-template-columns:1fr}}
.field label{display:block;font-weight:600;font-size:.92rem;margin-bottom:4px}
.field small{display:block;color:var(--muted);font-size:.8rem;margin-top:3px}
.field input,.field select{width:100%;padding:10px 12px;border:1px solid var(--line);border-radius:8px;background:var(--bg);color:var(--ink);font:inherit;min-height:44px}
.field input:focus,.field select:focus{outline:2px solid var(--brand);outline-offset:1px}
.field.full{grid-column:1/-1}
.check{display:flex;gap:8px;align-items:flex-start;font-size:.92rem}
.check input{margin-top:4px;width:18px;height:18px}
details.more{grid-column:1/-1;border-top:1px dashed var(--line);padding-top:10px}
details.more summary{cursor:pointer;font-weight:600;color:var(--brand)}
details.more .fields{margin-top:12px}
.btn{display:inline-block;background:var(--brand);color:var(--brand-ink);border:0;border-radius:10px;padding:12px 20px;font:inherit;font-weight:700;cursor:pointer;min-height:46px}
.btn:hover{filter:brightness(1.05)}
.actions{margin-top:16px;display:flex;gap:10px;flex-wrap:wrap}
.btn.ghost{background:transparent;color:var(--brand);border:1px solid var(--brand)}
.result{margin-top:18px;display:none}
.result.show{display:block}
.total{background:var(--brand-soft);border-radius:10px;padding:14px 16px;display:flex;justify-content:space-between;align-items:baseline;gap:10px;flex-wrap:wrap}
.total strong{font-size:1.6rem;color:var(--brand)}
table{width:100%;border-collapse:collapse;margin:12px 0;font-size:.95rem}
th,td{text-align:left;padding:9px 10px;border-bottom:1px solid var(--line);vertical-align:top}
th{font-size:.82rem;text-transform:uppercase;letter-spacing:.04em;color:var(--muted)}
td.num,th.num{text-align:right;white-space:nowrap}
.table-scroll{overflow-x:auto}
.note{background:var(--warn-bg);border:1px solid var(--warn-line);border-radius:10px;padding:12px 14px;font-size:.9rem;margin:14px 0}
.muted{color:var(--muted)}

/* sidebar */
.side{position:sticky;top:76px;display:grid;gap:16px}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px}
.card h3{margin:0 0 8px;font-size:1rem}
.card ul{margin:0;padding-left:18px}
.facts li{margin:4px 0}

/* ads: replace with AdSense units after approval */
.ad-slot{min-height:0}

/* faq */
.faq details{background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:12px 16px;margin:10px 0}
.faq summary{cursor:pointer;font-weight:600}
.faq details p{margin:.6em 0 0}

/* footer */
.site-footer{border-top:1px solid var(--line);background:var(--surface);padding:28px 0;font-size:.9rem;color:var(--muted)}
.site-footer .cols{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}
@media (max-width:700px){.site-footer .cols{grid-template-columns:1fr}}
.site-footer a{color:var(--muted)}
.site-footer ul{list-style:none;padding:0;margin:0}
.site-footer li{margin:4px 0}
@media print{.site-header,.site-footer,.side,.actions,.ad-slot{display:none}}
.items{width:100%;border-collapse:collapse}
.items td,.items th{padding:6px 4px;border-bottom:1px solid var(--line)}
.items input,.items select{width:100%;padding:8px;border:1px solid var(--line);border-radius:6px;background:var(--bg);color:var(--ink);font:inherit;min-height:40px}
.items .del{background:none;border:0;color:var(--accent);font-size:1.2rem;cursor:pointer}
@media (max-width:640px){.items thead{display:none}.items tr{display:grid;grid-template-columns:1fr 1fr;gap:6px;padding:8px 0;border-bottom:1px solid var(--line)}.items td{border:0;padding:0}.items td.name{grid-column:1/-1}}
/* Invoice preview / print */
.invoice{background:#fff;color:#111;border:1px solid #ccc;padding:28px;margin-top:20px;font-size:14px;line-height:1.6}
.invoice h2{text-align:center;letter-spacing:.5em;font-size:1.6rem;margin:0 0 18px;color:#111}
.inv-head{display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap}
.inv-to{font-size:1.15rem;border-bottom:1px solid #111;padding-bottom:4px;min-width:240px}
.inv-total{border:2px solid #111;padding:8px 14px;font-size:1.25rem;margin:14px 0;display:inline-block}
.invoice table th{color:#111;border-bottom:1px solid #111}
.invoice td,.invoice th{border-bottom:1px solid #ddd}
.inv-small{font-size:12px;color:#444}
@media print{
  body{background:#fff} main{padding:0} .no-print,.site-header,.site-footer,.breadcrumb,.ad-slot,.side,.calc,.content,h1,.lead,.updated{display:none!important}
  .invoice{display:block!important;border:0;margin:0;padding:0}
  .grid-2{display:block}
}
.invoice{overflow-x:auto}
@media (max-width:640px){.invoice{padding:16px;font-size:12px}.invoice h2{letter-spacing:.2em}.invoice td,.invoice th{padding:6px 4px}}