/* ============================================
   FLIP & STEEP — Aero-Technical Design System
   main.css — Tokens, Reset, Typography, Grid
   ============================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&family=Inter:wght@400;500;600&display=swap');

/* --- Design Tokens --- */
:root {
  /* Primary Palette */
  --color-primary: #000000;
  --color-on-primary: #ffffff;
  --color-primary-container: #1b1b1b;
  --color-on-primary-container: #848484;

  /* Secondary Palette (Signal Blue / Indigo) */
  --color-secondary: #4648D4;
  --color-secondary-bright: #6063EE;
  --color-on-secondary: #ffffff;
  --color-secondary-container: #6063ee;
  --color-on-secondary-container: #fffbff;

  /* Surface / Background */
  --color-background: #f8f9ff;
  --color-on-background: #0b1c30;
  --color-surface: #f8f9ff;
  --color-surface-dim: #cbdbf5;
  --color-surface-bright: #f8f9ff;
  --color-surface-container-lowest: #ffffff;
  --color-surface-container-low: #eff4ff;
  --color-surface-container: #e5eeff;
  --color-surface-container-high: #dce9ff;
  --color-surface-container-highest: #d3e4fe;

  /* On-Surface */
  --color-on-surface: #0b1c30;
  --color-on-surface-variant: #4c4546;

  /* Inverse */
  --color-inverse-surface: #213145;
  --color-inverse-on-surface: #eaf1ff;
  --color-inverse-primary: #c6c6c6;

  /* Outline */
  --color-outline: #7e7576;
  --color-outline-variant: #cfc4c5;

  /* Status */
  --color-error: #ba1a1a;
  --color-on-error: #ffffff;
  --color-success: #2E7D32;
  --color-on-success: #ffffff;

  /* Typography */
  --font-headline: 'Space Grotesk', sans-serif;
  --font-body: 'Inter', sans-serif;
  --font-label: 'Space Grotesk', sans-serif;

  /* Spacing */
  --space-unit: 4px;
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 80px;
  --space-5xl: 120px;
  --space-gutter: 24px;
  --space-margin: 64px;
  --container-max: 1440px;

  /* Border Radius */
  --radius-sm: 0.125rem;
  --radius-base: 0.25rem;
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-xl: 0.75rem;
  --radius-full: 9999px;

  /* Shadows (Ambient) */
  --shadow-sm: 0 1px 3px rgba(11, 28, 48, 0.04);
  --shadow-md: 0 4px 16px rgba(11, 28, 48, 0.06);
  --shadow-lg: 0 8px 32px rgba(11, 28, 48, 0.08);
  --shadow-xl: 0 16px 48px rgba(11, 28, 48, 0.10);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: 100px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-weight: 400;
  line-height: 1.6;
  color: var(--color-on-surface);
  background-color: var(--color-background);
  overflow-x: hidden;
}

img, video {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-fast);
}

button, input, select, textarea {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
  border: none;
  outline: none;
  background: none;
}

button {
  cursor: pointer;
}

ul, ol {
  list-style: none;
}

/* --- Selection Color --- */
::selection {
  background: rgba(70, 72, 212, 0.2);
  color: var(--color-on-surface);
}

::-moz-selection {
  background: rgba(70, 72, 212, 0.2);
  color: var(--color-on-surface);
}

/* --- Keyboard Focus Outlines (Accessibility) --- */
:focus-visible {
  outline: 2px solid var(--color-secondary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

:focus:not(:focus-visible) {
  outline: none;
}

/* --- Typography Scale --- */
.headline-xl {
  font-family: var(--font-headline);
  font-size: clamp(2.5rem, 5vw, 4.5rem);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.04em;
  color: var(--color-on-surface);
}

.headline-lg {
  font-family: var(--font-headline);
  font-size: clamp(2rem, 3.5vw, 3rem);
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--color-on-surface);
}

.headline-md {
  font-family: var(--font-headline);
  font-size: clamp(1.5rem, 2.5vw, 2rem);
  font-weight: 500;
  line-height: 1.3;
  color: var(--color-on-surface);
}

.body-lg {
  font-family: var(--font-body);
  font-size: 1.125rem;
  font-weight: 400;
  line-height: 1.6;
}

.body-md {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.6;
}

.label-caps {
  font-family: var(--font-label);
  font-size: 0.75rem;
  font-weight: 600;
  line-height: 1;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

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

.section {
  padding: var(--space-5xl) 0;
}

.section--tight {
  padding: var(--space-4xl) 0;
}

/* Grid */
.grid {
  display: grid;
  gap: var(--space-gutter);
}

.grid--2 { grid-template-columns: repeat(2, 1fr); }
.grid--3 { grid-template-columns: repeat(3, 1fr); }
.grid--4 { grid-template-columns: repeat(4, 1fr); }
.grid--12 { grid-template-columns: repeat(12, 1fr); }

/* Flex */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.flex-center { align-items: center; justify-content: center; }
.flex-between { justify-content: space-between; }
.flex-wrap { flex-wrap: wrap; }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }
.gap-lg { gap: var(--space-lg); }
.gap-xl { gap: var(--space-xl); }

/* Text Alignment */
.text-center { text-align: center; }
.text-left { text-align: left; }

/* --- Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-40px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes slideInRight {
  from {
    opacity: 0;
    transform: translateX(40px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

@keyframes countUp {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

@keyframes gradientShift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

@keyframes glowPulse {
  0%, 100% { box-shadow: 0 0 0 0 rgba(70, 72, 212, 0); }
  50% { box-shadow: 0 0 20px 4px rgba(70, 72, 212, 0.15); }
}

/* --- Page Loader --- */
.page-loader {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--color-background);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.4s ease, visibility 0.4s ease;
}

.page-loader.loaded {
  opacity: 0;
  visibility: hidden;
}

.page-loader__spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-outline-variant);
  border-top-color: var(--color-secondary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

/* --- Back to Top Button --- */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  z-index: 900;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-primary);
  color: var(--color-on-primary);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(16px) scale(0.8);
  transition: opacity var(--transition-base), visibility var(--transition-base), transform var(--transition-spring), background var(--transition-fast);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0) scale(1);
}

.back-to-top:hover {
  background: var(--color-secondary);
  transform: translateY(-2px) scale(1.05);
}

.back-to-top__icon {
  width: 20px;
  height: 20px;
  stroke: currentColor;
  stroke-width: 2.5;
  fill: none;
  transition: transform var(--transition-fast);
}

.back-to-top:hover .back-to-top__icon {
  transform: translateY(-2px);
}

/* Scroll Reveal */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.revealed {
  opacity: 1;
  transform: translateY(0);
}

.reveal-left {
  opacity: 0;
  transform: translateX(-40px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal-left.revealed {
  opacity: 1;
  transform: translateX(0);
}

.reveal-right {
  opacity: 0;
  transform: translateX(40px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal-right.revealed {
  opacity: 1;
  transform: translateX(0);
}

/* Stagger children */
.stagger-children .reveal:nth-child(1) { transition-delay: 0ms; }
.stagger-children .reveal:nth-child(2) { transition-delay: 100ms; }
.stagger-children .reveal:nth-child(3) { transition-delay: 200ms; }
.stagger-children .reveal:nth-child(4) { transition-delay: 300ms; }
.stagger-children .reveal:nth-child(5) { transition-delay: 400ms; }
.stagger-children .reveal:nth-child(6) { transition-delay: 500ms; }
.stagger-children .reveal:nth-child(7) { transition-delay: 600ms; }
.stagger-children .reveal:nth-child(8) { transition-delay: 700ms; }

/* --- Responsive --- */
@media (max-width: 1024px) {
  .container {
    padding: 0 var(--space-xl);
  }
  .grid--4 { grid-template-columns: repeat(2, 1fr); }
  .grid--3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .container {
    padding: 0 var(--space-lg);
  }
  .section {
    padding: var(--space-4xl) 0;
  }
  .grid--4,
  .grid--3,
  .grid--2 {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-md);
  }
  .section {
    padding: var(--space-3xl) 0;
  }
}