/* ============================================
   High School GPA Calculator — Soft Dark Mode
   Mobile-first, modular CSS
   ============================================ */

:root {
  --bg-primary: #1a1d2e;
  --bg-secondary: #252836;
  --bg-card: #2d3142;
  --text-primary: #f0f2f5;
  --text-muted: #a0a4b0;
  --accent: #6ee7b7;
  --accent-hover: #5dd9a8;
  --accent-glow: rgba(110, 231, 183, 0.35);
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.25);
  --transition: 0.2s ease;
}

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

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, sans-serif;
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text-primary);
  background: var(--bg-primary);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* --- Header --- */
.site-header {
  text-align: center;
  padding: 2rem 1.25rem 1.5rem;
  max-width: 640px;
  margin: 0 auto;
}

.site-header h1 {
  margin: 0 0 0.5rem;
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

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

/* --- Calculator card --- */
.calculator-wrapper {
  padding: 0 1.25rem 2rem;
  max-width: 640px;
  margin: 0 auto;
}

.calculator-card {
  background: var(--bg-card);
  border-radius: var(--border-radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.classes-container {
  margin-bottom: 1.5rem;
}

.class-rows {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.class-row {
  display: grid;
  grid-template-columns: 1fr 1fr auto auto;
  gap: 0.5rem;
  align-items: center;
  padding: 0.75rem;
  background: var(--bg-secondary);
  border-radius: var(--border-radius-sm);
  border: 1px solid transparent;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.class-row:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--accent-glow);
}

/* Form controls — shared */
select,
input[type="number"] {
  width: 100%;
  min-width: 0;
  padding: 0.6rem 0.75rem;
  font-size: 0.95rem;
  font-family: inherit;
  color: var(--text-primary);
  background: var(--bg-primary);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--border-radius-sm);
  transition: border-color var(--transition), background var(--transition);
  -webkit-appearance: none;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23a0a4b0' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  padding-right: 2rem;
}

input[type="number"] {
  background-image: none;
  padding-right: 0.75rem;
}

select:hover,
input[type="number"]:hover {
  border-color: rgba(255, 255, 255, 0.2);
}

select:focus,
input[type="number"]:focus {
  outline: none;
  border-color: var(--accent);
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  opacity: 1;
}

/* Credits column — narrower */
.class-row .credits-input {
  max-width: 5rem;
  text-align: center;
}

/* Remove class button */
.btn-remove {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.25rem;
  height: 2.25rem;
  padding: 0;
  font-size: 1.1rem;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: color var(--transition), background var(--transition), border-color var(--transition);
  flex-shrink: 0;
}

.btn-remove:hover,
.btn-remove:focus {
  color: #f87171;
  background: rgba(248, 113, 113, 0.1);
  border-color: rgba(248, 113, 113, 0.3);
  outline: none;
}

/* Add class button */
.btn-add {
  width: 100%;
  padding: 0.85rem 1.25rem;
  font-size: 1rem;
  font-weight: 600;
  color: var(--bg-primary);
  background: var(--accent);
  border: none;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
}

.btn-add:hover,
.btn-add:focus {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px var(--accent-glow);
  outline: none;
}

.btn-add:active {
  transform: translateY(0);
}

/* --- GPA display --- */
.gpa-display {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.gpa-box {
  text-align: center;
  padding: 1.25rem 1rem;
  background: var(--bg-secondary);
  border-radius: var(--border-radius-sm);
  border: 1px solid rgba(255, 255, 255, 0.06);
}

.gpa-label {
  display: block;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.35rem;
}

.gpa-value {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: -0.02em;
}

.gpa-scale {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* --- Article --- */
.content-article {
  max-width: 720px;
  margin: 0 auto;
  padding: 2rem 1.25rem 3rem;
}

.content-article h2 {
  font-size: 1.5rem;
  margin: 0 0 1rem;
  color: var(--text-primary);
}

.content-article h3 {
  font-size: 1.2rem;
  margin: 1.75rem 0 0.6rem;
  color: var(--text-primary);
}

.content-article p {
  margin: 0 0 1.25rem;
  color: var(--text-muted);
  line-height: 1.75;
}

/* --- Footer --- */
.site-footer {
  text-align: center;
  padding: 1.5rem 1.25rem;
  background: var(--bg-secondary);
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1rem 1.5rem;
  margin-bottom: 1rem;
}

.footer-nav a {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.95rem;
  transition: color var(--transition);
}

.footer-nav a:hover,
.footer-nav a:focus {
  color: var(--accent-hover);
  text-decoration: underline;
  outline: none;
}

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

/* --- Mobile: stack class row on very small screens --- */
@media (max-width: 420px) {
  .class-row {
    grid-template-columns: 1fr 1fr;
    grid-template-rows: auto auto;
  }

  .class-row .credits-input {
    max-width: none;
    grid-column: 1;
  }

  .class-row .btn-remove {
    grid-column: 2;
    justify-self: end;
  }
}

/* --- Tablet and up --- */
@media (min-width: 600px) {
  .site-header h1 {
    font-size: 2rem;
  }

  .calculator-card {
    padding: 2rem;
  }

  .gpa-value {
    font-size: 2.25rem;
  }

  .content-article h2 {
    font-size: 1.65rem;
  }

  .content-article h3 {
    font-size: 1.25rem;
  }
}