:root {
  --bg-deep: #0f1412;
  --bg-mid: #17201c;
  --surface: rgba(28, 40, 35, 0.88);
  --border: rgba(180, 210, 195, 0.12);
  --text: #eef6f1;
  --text-muted: #8fa89a;
  --accent: #3ecf8e;
  --accent-soft: rgba(62, 207, 142, 0.14);
  --accent-strong: #2bb673;
  --warn: #e8b86d;
  --radius: 14px;
  --radius-sm: 8px;
  --font-body: "Outfit", system-ui, sans-serif;
  --font-display: "Syne", Georgia, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;
  --shadow: 0 18px 48px rgba(0, 0, 0, 0.4);
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.55;
  color: var(--text);
  background: var(--bg-deep);
  background-image:
    radial-gradient(ellipse 80% 45% at 10% -10%, rgba(62, 207, 142, 0.16), transparent 55%),
    radial-gradient(ellipse 60% 40% at 95% 10%, rgba(70, 140, 120, 0.12), transparent 50%),
    linear-gradient(165deg, var(--bg-deep), var(--bg-mid) 50%, #0c110f);
  background-attachment: fixed;
}

.page {
  max-width: 720px;
  margin: 0 auto;
  padding: 1.25rem 1.25rem 3rem;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.top {
  margin-bottom: 1.75rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.top__inner {
  margin-bottom: 0.85rem;
}

.brand {
  font-family: var(--font-display);
  font-size: clamp(1.75rem, 4vw, 2.15rem);
  font-weight: 700;
  margin: 0 0 0.3rem;
  letter-spacing: -0.03em;
}

.tag {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.98rem;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}

.nav__link {
  color: var(--text-muted);
  text-decoration: none;
  padding: 0.4rem 0.85rem;
  border-radius: 999px;
  border: 1px solid transparent;
  font-weight: 500;
  font-size: 0.9rem;
  transition: color 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}

.nav__link:hover {
  color: var(--text);
  background: rgba(255, 255, 255, 0.04);
}

.nav__link--active {
  color: var(--text);
  border-color: var(--border);
  background: var(--accent-soft);
}

.main {
  flex: 1;
}

.lead {
  margin: 0 0 1.35rem;
  color: var(--text-muted);
  font-size: 1.02rem;
  max-width: 36rem;
}

.calc-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.calc-list__link {
  display: block;
  text-decoration: none;
  color: inherit;
  padding: 1.1rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  transition: border-color 0.15s ease, transform 0.15s ease, background 0.15s ease;
}

.calc-list__link:hover {
  border-color: rgba(62, 207, 142, 0.35);
  background: rgba(34, 48, 42, 0.95);
  transform: translateY(-1px);
}

.calc-list__title {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 700;
  margin: 0 0 0.25rem;
  letter-spacing: -0.02em;
}

.calc-list__desc {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.92rem;
}

.calc {
  display: flex;
  flex-direction: column;
  gap: 1.35rem;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.field__label {
  font-weight: 600;
  font-size: 0.92rem;
}

.field__hint {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.82rem;
}

.field-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  align-items: stretch;
  max-width: 28rem;
}

.field__input,
.field__select {
  font-family: var(--font-mono);
  font-size: 1.15rem;
  padding: 0.75rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(10, 14, 12, 0.65);
  color: var(--text);
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.field__input {
  width: 100%;
  max-width: 20rem;
}

.field__input--grow {
  flex: 1 1 8rem;
  min-width: 7rem;
  max-width: none;
  width: auto;
}

.field__select {
  flex: 0 1 9.5rem;
  min-width: 7.5rem;
  cursor: pointer;
  appearance: none;
  background-image:
    linear-gradient(45deg, transparent 50%, var(--text-muted) 50%),
    linear-gradient(135deg, var(--text-muted) 50%, transparent 50%);
  background-position:
    calc(100% - 1.15rem) calc(50% - 0.15rem),
    calc(100% - 0.75rem) calc(50% - 0.15rem);
  background-size: 0.4rem 0.4rem, 0.4rem 0.4rem;
  background-repeat: no-repeat;
  padding-right: 2.1rem;
}

.field__select option {
  background: #17201c;
  color: var(--text);
}

.field__input:focus,
.field__select:focus {
  border-color: rgba(62, 207, 142, 0.55);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.field__input::placeholder {
  color: rgba(143, 168, 154, 0.55);
}

.field__input:invalid:not(:placeholder-shown):not(:focus) {
  border-color: rgba(232, 184, 109, 0.55);
}

.result {
  margin-top: 0.35rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
}

.result__label {
  margin: 0 0 0.35rem;
  color: var(--text-muted);
  font-size: 0.88rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.result__value {
  font-family: var(--font-display);
  font-size: clamp(2rem, 6vw, 2.75rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  margin: 0;
  color: var(--accent);
  line-height: 1.15;
  transition: opacity 0.15s ease;
}

.result__value--empty {
  color: var(--text-muted);
  font-size: clamp(1.35rem, 4vw, 1.75rem);
  font-weight: 600;
}

.result__formula {
  margin: 0.55rem 0 0;
  font-family: var(--font-mono);
  font-size: 0.92rem;
  color: var(--text-muted);
  min-height: 1.4em;
}

.result__extras {
  margin-top: 0.9rem;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.result__meta {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.foot {
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

.foot__muted {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.85rem;
}

@media (prefers-reduced-motion: reduce) {
  .calc-list__link,
  .nav__link,
  .field__input,
  .field__select,
  .result__value {
    transition: none;
  }

  .calc-list__link:hover {
    transform: none;
  }
}