/* ============================================
   AI Builder Institute — Styles
   Mobile-first responsive design
   ============================================ */

/* --- Reset & Base --- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --color-bg: #0b1120;
  --color-bg-alt: #111827;
  --color-surface: #1e293b;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-heading: #f1f5f9;
  --color-accent: #3b82f6;
  --color-accent-hover: #2563eb;
  --color-accent-glow: rgba(59, 130, 246, 0.15);
  --color-border: #1e293b;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --container-max: 1120px;
  --radius: 8px;
  --radius-lg: 12px;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration: none;
}

img {
  max-width: 100%;
  display: block;
}

/* --- Layout --- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 20px;
}

.container--narrow {
  max-width: 600px;
}

/* --- Buttons --- */
.btn {
  display: inline-block;
  padding: 14px 32px;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s, transform 0.2s;
  text-align: center;
}

.btn--primary {
  background: var(--color-accent);
  color: #fff;
}

.btn--primary:hover {
  background: var(--color-accent-hover);
  transform: translateY(-1px);
}

.btn--full {
  width: 100%;
}

/* --- Navigation --- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(11, 17, 32, 0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
}

.nav__container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 20px;
  height: 64px;
}

.nav__logo {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-heading);
  letter-spacing: -0.02em;
}

.nav__logo:hover {
  color: var(--color-accent);
}

.nav__toggle {
  display: flex;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav__toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

.nav__toggle.active span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav__toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav__toggle.active span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.nav__menu {
  display: none;
  list-style: none;
  position: absolute;
  top: 64px;
  left: 0;
  right: 0;
  background: var(--color-bg-alt);
  border-bottom: 1px solid var(--color-border);
  padding: 16px 20px;
}

.nav__menu.active {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.nav__link {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  padding: 8px 0;
  display: block;
  transition: color 0.2s;
}

.nav__link:hover {
  color: var(--color-heading);
}

.nav__link--cta {
  color: var(--color-accent);
  font-weight: 600;
}

/* --- Hero --- */
.hero {
  padding: 140px 0 80px;
  text-align: center;
  background: linear-gradient(180deg, var(--color-bg) 0%, var(--color-bg-alt) 100%);
}

.hero__title {
  font-size: 2.5rem;
  font-weight: 800;
  line-height: 1.15;
  color: var(--color-heading);
  letter-spacing: -0.03em;
  margin-bottom: 20px;
}

.hero__subtitle {
  font-size: 1.15rem;
  color: var(--color-text-muted);
  max-width: 560px;
  margin: 0 auto 36px;
  line-height: 1.6;
}

/* --- Sections --- */
.section {
  padding: 80px 0;
}

.section--alt {
  background: var(--color-bg-alt);
}

.section__title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-heading);
  letter-spacing: -0.02em;
  margin-bottom: 16px;
  text-align: center;
}

.section__subtitle {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  text-align: center;
  max-width: 520px;
  margin: 0 auto 40px;
}

/* --- Problem Section --- */
.problem__grid {
  display: grid;
  gap: 20px;
  margin-top: 40px;
}

.problem__card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
}

.problem__card h3 {
  font-size: 1.15rem;
  color: var(--color-heading);
  margin-bottom: 10px;
}

.problem__card p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* --- Bootcamp Section --- */
.bootcamp__grid {
  display: grid;
  gap: 20px;
  margin-top: 40px;
}

.bootcamp__day {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
}

.bootcamp__day h3 {
  font-size: 1.15rem;
  color: var(--color-heading);
  margin-bottom: 16px;
}

.bootcamp__list {
  list-style: none;
  padding: 0;
}

.bootcamp__list li {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.6;
  padding: 6px 0 6px 20px;
  position: relative;
}

.bootcamp__list li::before {
  content: "\2192";
  position: absolute;
  left: 0;
  color: var(--color-accent);
}

.bootcamp__cta {
  text-align: center;
  margin-top: 40px;
}

.bootcamp__cta p {
  color: var(--color-text-muted);
  margin-bottom: 20px;
  font-size: 1.05rem;
}

/* --- Why Us Section --- */
.why__content {
  margin-top: 40px;
}

.why__item {
  margin-bottom: 32px;
}

.why__item h3 {
  font-size: 1.15rem;
  color: var(--color-heading);
  margin-bottom: 8px;
}

.why__item p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.6;
}

.why__stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 16px;
}

.stat {
  text-align: center;
  padding: 24px 12px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
}

.stat__number {
  display: block;
  font-size: 2rem;
  font-weight: 800;
  color: var(--color-accent);
  letter-spacing: -0.02em;
}

.stat__label {
  display: block;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: 4px;
}

/* --- Form --- */
.form {
  margin-top: 8px;
}

.form__group {
  margin-bottom: 20px;
}

.form__label {
  display: block;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text);
  margin-bottom: 6px;
}

.form__input {
  width: 100%;
  padding: 12px 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  color: var(--color-text);
  font-size: 1rem;
  font-family: var(--font-sans);
  transition: border-color 0.2s;
}

.form__input:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-glow);
}

.form__input option {
  background: var(--color-surface);
}

.form__success {
  text-align: center;
  padding: 24px;
  background: rgba(59, 130, 246, 0.1);
  border: 1px solid var(--color-accent);
  border-radius: var(--radius-lg);
  color: var(--color-heading);
  font-weight: 500;
  margin-top: 16px;
}

/* --- Footer --- */
.footer {
  padding: 48px 0 24px;
  border-top: 1px solid var(--color-border);
}

.footer__content {
  display: flex;
  flex-direction: column;
  gap: 24px;
  margin-bottom: 32px;
}

.footer__logo {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-heading);
}

.footer__tagline {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-top: 6px;
}

.footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.footer__links a {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  transition: color 0.2s;
}

.footer__links a:hover {
  color: var(--color-heading);
}

.footer__bottom {
  border-top: 1px solid var(--color-border);
  padding-top: 20px;
}

.footer__bottom p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* ============================================
   Tablet (640px+)
   ============================================ */
@media (min-width: 640px) {
  .problem__grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .bootcamp__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .footer__content {
    flex-direction: row;
    justify-content: space-between;
    align-items: flex-start;
  }
}

/* ============================================
   Desktop (900px+)
   ============================================ */
@media (min-width: 900px) {
  .nav__toggle {
    display: none;
  }

  .nav__menu {
    display: flex;
    position: static;
    background: none;
    border: none;
    padding: 0;
    gap: 32px;
    align-items: center;
  }

  .hero {
    padding: 180px 0 120px;
  }

  .hero__title {
    font-size: 3.5rem;
  }

  .hero__subtitle {
    font-size: 1.25rem;
  }

  .section {
    padding: 100px 0;
  }

  .section__title {
    font-size: 2.25rem;
  }

  .bootcamp__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .why__content {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 60px;
    align-items: start;
  }
}