@import url('https://fonts.googleapis.com/css2?family=Zen+Kaku+Gothic+New:wght@500;700;900&family=Noto+Sans+JP:wght@400;500;700&display=swap');

:root{
  --bg:#F7F8FB;
  --surface:#FFFFFF;
  --ink:#1F2933;
  --ink-soft:#5A6472;
  --accent:#2B4C7E;
  --accent-soft:#E7ECF3;
  --result:#B9761F;
  --result-bg:#FBF1E1;
  --border:#D7DEE8;
  --grid:#E2E8F1;
  --maxw:760px;
}

*{box-sizing:border-box;}
html{-webkit-text-size-adjust:100%;}
body{
  margin:0;
  color:var(--ink);
  font-family:'Noto Sans JP', sans-serif;
  line-height:1.75;
  background-color:var(--bg);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size:28px 28px;
  background-position:-1px -1px;
}

a{color:var(--accent);}
a:focus-visible, button:focus-visible, input:focus-visible{
  outline:3px solid var(--accent);
  outline-offset:2px;
}

.wrap{max-width:var(--maxw); margin:0 auto; padding:0 20px;}

header.site-header{
  background:var(--surface);
  border-bottom:1px solid var(--border);
  position:sticky; top:0; z-index:10;
}
header.site-header .wrap{
  display:flex; align-items:center; justify-content:space-between;
  padding-top:14px; padding-bottom:14px;
  max-width:920px;
}
.brand{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-weight:900;
  font-size:1.05rem;
  color:var(--ink);
  text-decoration:none;
  letter-spacing:.01em;
}
.brand span{color:var(--accent);}
nav.top-nav a{
  margin-left:16px;
  font-size:.9rem;
  color:var(--ink-soft);
  text-decoration:none;
}
nav.top-nav a:hover{color:var(--accent);}

main{max-width:920px; margin:0 auto; padding:36px 20px 60px;}

.hero{padding:20px 0 8px;}
.hero h1{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-weight:900;
  font-size:2rem;
  line-height:1.4;
  margin:0 0 10px;
  max-width:16ch;
}
.hero p{color:var(--ink-soft); max-width:44ch; margin:0 0 28px;}

.grid{
  display:grid;
  grid-template-columns:repeat(auto-fill, minmax(200px,1fr));
  gap:14px;
  margin:24px 0 40px;
}
.card{
  background:var(--surface);
  border:1px solid var(--border);
  border-left:4px solid var(--accent);
  padding:16px 18px;
  text-decoration:none;
  color:var(--ink);
  display:block;
}
.card h3{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-size:1.02rem;
  margin:0 0 6px;
}
.card p{font-size:.86rem; color:var(--ink-soft); margin:0;}

.category-label{
  font-size:.82rem;
  color:var(--ink-soft);
  margin:34px 0 10px;
  padding-bottom:6px;
  border-bottom:1px solid var(--border);
}

.calc-title{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-weight:900;
  font-size:1.6rem;
  margin:0 0 8px;
  max-width:18ch;
}
.calc-lead{color:var(--ink-soft); max-width:52ch; margin:0 0 26px;}

.calc-card{
  background:var(--surface);
  border:1px solid var(--border);
  border-left:4px solid var(--accent);
  padding:26px 24px;
  margin-bottom:28px;
}

.field{margin-bottom:18px;}
.field label{
  display:block;
  font-size:.88rem;
  color:var(--ink-soft);
  margin-bottom:6px;
}
.field .row{display:flex; gap:10px; flex-wrap:wrap;}
.field input, .field select{
  width:100%;
  font-size:1.05rem;
  font-family:'Noto Sans JP', sans-serif;
  padding:10px 4px;
  border:none;
  border-bottom:2px solid var(--border);
  background:transparent;
  color:var(--ink);
}
.field input:focus, .field select:focus{border-bottom-color:var(--accent);}
.field .unit{align-self:center; color:var(--ink-soft); font-size:.9rem; white-space:nowrap;}

button.calc-btn{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-weight:700;
  font-size:1rem;
  background:var(--accent);
  color:#fff;
  border:none;
  padding:13px 26px;
  cursor:pointer;
  margin-top:4px;
}
button.calc-btn:hover{background:#233d64;}

.result{
  margin-top:22px;
  padding:18px 20px;
  background:var(--result-bg);
  border-left:4px solid var(--result);
  display:none;
}
.result.show{display:block;}
.result .num{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-weight:900;
  font-size:2rem;
  color:var(--result);
  line-height:1.2;
}
.result .label{font-size:.85rem; color:var(--ink-soft); margin-top:2px;}

.explain{max-width:64ch;}
.explain h2{
  font-family:'Zen Kaku Gothic New', sans-serif;
  font-size:1.1rem;
  margin:32px 0 10px;
}
.explain p{color:var(--ink); font-size:.95rem;}

.related{margin-top:40px;}
.disclaimer{
  margin-top:36px;
  font-size:.82rem;
  color:var(--ink-soft);
  border-top:1px solid var(--border);
  padding-top:14px;
}

footer.site-footer{
  border-top:1px solid var(--border);
  margin-top:40px;
  padding:24px 0 40px;
  color:var(--ink-soft);
  font-size:.85rem;
}
footer.site-footer .wrap{max-width:920px; display:flex; gap:18px; flex-wrap:wrap;}
footer.site-footer a{color:var(--ink-soft);}

@media (max-width:520px){
  .hero h1{font-size:1.6rem;}
  .calc-title{font-size:1.35rem;}
}