@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@500;600;700&family=IBM+Plex+Sans:wght@400;500;600;700&display=swap');

:root{
  --paper:#F5F6F2;
  --paper-line:#DCE1DA;
  --ink:#13202B;
  --ink-soft:#3E4C56;
  --amber:#F5A623;
  --amber-deep:#C97F0B;
  --teal:#1F8A70;
  --card:#FFFFFF;
  --border:#D8DEDA;
}
*{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  font-family:'IBM Plex Sans',-apple-system,sans-serif;
  color:var(--ink);
  line-height:1.55;
  background-color:var(--paper);
  background-image:
    linear-gradient(var(--paper-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--paper-line) 1px, transparent 1px);
  background-size:28px 28px;
  background-position:-1px -1px;
}
::selection{background:var(--amber);color:var(--ink);}

header{
  background:var(--ink);
  color:#fff;
  padding:18px 28px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  flex-wrap:wrap;
  border-bottom:3px solid var(--amber);
}
header a{color:#fff;text-decoration:none;}
.logo{
  font-family:'IBM Plex Mono',monospace;
  font-weight:700;
  font-size:1.35rem;
  letter-spacing:-.02em;
}
.logo span{color:var(--amber);}
nav a{margin-left:22px;color:#B9C4CC;font-size:.92rem;font-weight:500;}
nav a:hover{color:var(--amber);}

.container{max-width:980px;margin:0 auto;padding:36px 20px;}

.hero{text-align:center;padding:56px 20px 24px;}
.eyebrow{
  font-family:'IBM Plex Mono',monospace;
  font-size:.78rem;
  letter-spacing:.14em;
  text-transform:uppercase;
  color:var(--amber-deep);
  font-weight:600;
  margin-bottom:14px;
  display:inline-block;
}
.hero h1{
  font-family:'IBM Plex Mono',monospace;
  font-size:2.4rem;
  font-weight:700;
  letter-spacing:-.02em;
  margin-bottom:14px;
  line-height:1.15;
}
.hero p{color:var(--ink-soft);font-size:1.08rem;max-width:600px;margin:0 auto;}

.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:22px;margin-top:36px;}

.card{
  position:relative;
  background:var(--card);
  border:1px solid var(--border);
  padding:22px 20px 24px;
  text-decoration:none;
  color:var(--ink);
  box-shadow:0 2px 0 var(--border);
  transition:transform .15s ease, box-shadow .15s ease;
  --notch: 10px;
  clip-path: polygon(
    0% var(--notch), 5% 0%, 10% var(--notch), 15% 0%, 20% var(--notch), 25% 0%, 30% var(--notch), 35% 0%, 40% var(--notch), 45% 0%, 50% var(--notch), 55% 0%, 60% var(--notch), 65% 0%, 70% var(--notch), 75% 0%, 80% var(--notch), 85% 0%, 90% var(--notch), 95% 0%, 100% var(--notch),
    100% 100%, 0% 100%
  );
}
.card:hover{transform:translateY(-4px);box-shadow:0 8px 0 var(--border);}
.card .num{
  font-family:'IBM Plex Mono',monospace;
  font-size:.75rem;
  color:var(--amber-deep);
  font-weight:600;
  display:block;
  margin-bottom:6px;
}
.card h3{font-size:1.08rem;margin-bottom:6px;font-weight:600;}
.card p{color:var(--ink-soft);font-size:.9rem;}

.tool-box{
  background:var(--card);
  border:1px solid var(--border);
  border-top:4px solid var(--ink);
  padding:30px;
  max-width:600px;
  margin:26px auto;
  box-shadow:0 3px 0 var(--border);
}
label{
  display:block;
  font-family:'IBM Plex Mono',monospace;
  font-weight:600;
  font-size:.82rem;
  margin:16px 0 6px;
  color:var(--ink-soft);
  text-transform:uppercase;
  letter-spacing:.03em;
}
input,select{
  width:100%;
  padding:11px 12px;
  border:1.5px solid var(--border);
  background:var(--paper);
  font-family:'IBM Plex Mono',monospace;
  font-size:1rem;
  color:var(--ink);
}
input:focus,select:focus{outline:none;border-color:var(--amber-deep);}

button.calc-btn{
  margin-top:24px;
  width:100%;
  padding:14px;
  background:var(--amber);
  color:var(--ink);
  border:2px solid var(--ink);
  font-family:'IBM Plex Mono',monospace;
  font-size:1rem;
  font-weight:700;
  text-transform:uppercase;
  letter-spacing:.04em;
  cursor:pointer;
  box-shadow:3px 3px 0 var(--ink);
  transition:transform .1s ease, box-shadow .1s ease;
}
button.calc-btn:hover{transform:translate(2px,2px);box-shadow:1px 1px 0 var(--ink);}
button.calc-btn:active{transform:translate(3px,3px);box-shadow:0 0 0 var(--ink);}

.result{
  margin-top:22px;
  padding:18px;
  background:var(--ink);
  color:#fff;
  border:none;
  font-family:'IBM Plex Mono',monospace;
  display:none;
}
.result.show{display:block;}
.result-row{display:flex;justify-content:space-between;padding:5px 0;font-size:.95rem;}
.result-row strong{color:var(--amber);font-weight:600;}

.explain{max-width:680px;margin:40px auto 0;color:var(--ink-soft);font-size:.95rem;}
.explain h2{
  font-family:'IBM Plex Mono',monospace;
  color:var(--ink);
  font-size:1.05rem;
  margin-bottom:10px;
  font-weight:600;
}

footer{
  text-align:center;
  padding:34px 20px;
  color:var(--ink-soft);
  font-size:.85rem;
  border-top:1px solid var(--border);
  margin-top:48px;
  font-family:'IBM Plex Mono',monospace;
}
footer a{color:var(--ink-soft);}
footer a:hover{color:var(--amber-deep);}