*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --color-bg: #f9fafb;
  --color-surface: #ffffff;
  --color-border: #e5e7eb;
  --color-text: #111827;
  --color-muted: #6b7280;
  --color-accent: #2563eb;
  --color-accent-light: #eff6ff;
  --color-result-bg: #f0fdf4;
  --color-result-border: #86efac;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,.08);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  font-size: 16px;
}

a { color: var(--color-accent); }

/* Layout */
.site-header { background: var(--color-surface); border-bottom: 1px solid var(--color-border); padding: 14px 20px; }
.site-header h1 { font-size: 1.1rem; font-weight: 600; }

.container { max-width: 680px; margin: 0 auto; padding: 0 16px; }

main { padding: 32px 0 48px; }

.intro { margin-bottom: 28px; }
.intro h2 { font-size: 1.5rem; font-weight: 700; margin-bottom: 8px; }
.intro p { color: var(--color-muted); max-width: 540px; }

/* Ad slot */
.ad-slot { background: var(--color-border); border-radius: var(--radius); height: 90px; display: flex; align-items: center; justify-content: center; color: var(--color-muted); font-size: .85rem; margin-bottom: 28px; }

/* Calculator card */
.calc-card { background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); margin-bottom: 24px; }

.field { margin-bottom: 20px; }
.field label { display: block; font-weight: 500; font-size: .9rem; margin-bottom: 6px; }
.field .hint { font-size: .8rem; color: var(--color-muted); margin-top: 4px; }

.input-wrap { position: relative; }
.input-prefix { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--color-muted); font-weight: 500; pointer-events: none; }

input[type="number"] {
  width: 100%;
  padding: 10px 12px 10px 28px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 1rem;
  color: var(--color-text);
  background: var(--color-bg);
  -moz-appearance: textfield;
}
input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button { -webkit-appearance: none; }
input[type="number"]:focus { outline: 2px solid var(--color-accent); outline-offset: 1px; border-color: transparent; }

.toggle-field { display: flex; align-items: center; gap: 10px; margin-bottom: 20px; }
.toggle-field label { font-weight: 500; font-size: .9rem; cursor: pointer; }
input[type="checkbox"] { width: 18px; height: 18px; accent-color: var(--color-accent); cursor: pointer; }

/* Output */
#output { background: var(--color-result-bg); border: 1px solid var(--color-result-border); border-radius: var(--radius); padding: 20px 24px; margin-top: 8px; transition: opacity .15s; }
#output[aria-hidden="true"] { opacity: .4; pointer-events: none; }

.result-label { font-size: .85rem; color: var(--color-muted); text-transform: uppercase; letter-spacing: .05em; margin-bottom: 4px; }
#result-rate { font-size: 2.4rem; font-weight: 800; color: var(--color-accent); margin-bottom: 16px; }

#result-breakdown { list-style: none; display: flex; flex-direction: column; gap: 6px; font-size: .95rem; color: var(--color-muted); }
#result-breakdown strong { color: var(--color-text); }

/* Sections below fold */
.section { margin-top: 40px; }
.section h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 12px; }
.how-it-works { list-style: none; display: flex; flex-direction: column; gap: 10px; }
.how-it-works li { display: flex; gap: 12px; font-size: .95rem; }
.how-it-works .step-num { font-weight: 700; color: var(--color-accent); min-width: 20px; }

.faq { display: flex; flex-direction: column; gap: 20px; }
.faq-item dt { font-weight: 600; margin-bottom: 4px; }
.faq-item dd { color: var(--color-muted); font-size: .95rem; }

/* Footer */
.site-footer { border-top: 1px solid var(--color-border); padding: 20px; text-align: center; font-size: .85rem; color: var(--color-muted); margin-top: 48px; }

@media (max-width: 480px) {
  #result-rate { font-size: 2rem; }
  .calc-card { padding: 16px; }
}