/* ==========================================================================
   MAIN CORE STYLES & LAYOUT
   Oshan Nethsara Subhasinghe — Personal Portfolio (oshan.me)
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Bricolage+Grotesque:opsz,wght@12..96,400..800&family=Plus+Jakarta+Sans:ital,wght@0,300..800;1,400..700&family=IBM+Plex+Mono:wght@400;500;600&display=swap');

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

html {
  scroll-behavior: smooth;
}

body {
  background-color: var(--bg);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  position: relative;
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

::selection {
  background: var(--amber);
  color: #fff;
}

[data-theme="dark"] ::selection {
  background: var(--amber);
  color: #0c0e12;
}

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

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

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

.mono {
  font-family: var(--font-mono);
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  letter-spacing: -0.02em;
  font-weight: 700;
  line-height: 1.1;
}

/* Top Progress Bar */
.top-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 2px;
  width: 0%;
  background: linear-gradient(90deg, var(--amber), var(--cyan));
  z-index: 100;
  transition: width 0.08s linear;
}

/* Left Rail Navigation */
.rail {
  position: fixed;
  left: 0;
  top: 0;
  bottom: 0;
  width: var(--rail-w);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  padding: 28px 0;
  z-index: 50;
  border-right: 1px solid var(--line);
  background: var(--bg);
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.rail-logo {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 11.5px;
  letter-spacing: 0.14em;
  color: var(--text-muted);
  writing-mode: vertical-rl;
  text-transform: uppercase;
  transform: rotate(180deg);
  transition: color var(--transition-fast);
}
.rail-logo:hover {
  color: var(--amber);
}

.rail-track {
  position: relative;
  flex: 1;
  width: 1px;
  background: var(--line);
  margin: 16px 0;
}

.rail-fill {
  position: absolute;
  top: 0;
  left: 0;
  width: 1px;
  height: 0%;
  background: var(--amber);
}

.rail-dot {
  position: absolute;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--surface-raised);
  border: 1px solid var(--line-light);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.rail-dot:hover {
  border-color: var(--amber);
  transform: translate(-50%, -50%) scale(1.3);
}

.rail-dot.active {
  background: var(--amber);
  border-color: var(--amber);
  box-shadow: 0 0 0 3px var(--amber-dim);
}

.rail-code {
  font-size: 9px;
  color: var(--text-muted);
  letter-spacing: 0.05em;
}

/* Top Floating Header */
.topnav {
  position: fixed;
  top: 0;
  right: 0;
  left: var(--rail-w);
  height: var(--header-h);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 40px;
  z-index: 40;
  pointer-events: none;
  background: linear-gradient(180deg, var(--bg) 0%, transparent 100%);
  transition: background-color var(--transition-normal);
}

.topnav * {
  pointer-events: auto;
}

.brand {
  font-family: var(--font-display);
  font-weight: 750;
  font-size: 16px;
  letter-spacing: -0.01em;
  color: var(--text-primary);
  display: inline-flex;
  align-items: center;
}

.brand .dot {
  color: var(--amber);
}

.topnav-actions {
  display: flex;
  align-items: center;
  gap: 14px;
}

.nav-links {
  display: flex;
  gap: 22px;
  list-style: none;
}

.nav-link {
  font-size: 13.5px;
  color: var(--text-secondary);
}

.nav-link:hover {
  color: var(--text-primary);
}

.theme-toggle-btn {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--surface);
  border: 1px solid var(--line);
  color: var(--text-primary);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  border-color: var(--amber);
  color: var(--amber);
}

.theme-toggle-btn svg {
  width: 16px;
  height: 16px;
}

.theme-icon-light {
  display: none;
}

[data-theme="light"] .theme-icon-dark {
  display: none;
}

[data-theme="light"] .theme-icon-light {
  display: block;
}

.nav-cta {
  font-size: 13px;
  font-weight: 600;
  padding: 8px 18px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.nav-cta:hover {
  border-color: var(--amber);
  color: var(--amber);
}

/* Shell & Sections */
.shell {
  margin-left: var(--rail-w);
}

section {
  padding: 120px 40px;
  max-width: var(--content-max);
  margin: 0 auto;
  border-bottom: 1px solid var(--line);
}

section:last-of-type {
  border-bottom: none;
}

.sec-tag {
  display: flex;
  align-items: baseline;
  gap: 14px;
  margin-bottom: 28px;
  color: var(--text-muted);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.1em;
}

.sec-tag .num {
  color: var(--amber);
}

.sec-tag .rule {
  flex: 1;
  height: 1px;
  background: var(--line);
}

.btn {
  font-size: 14px;
  font-weight: 600;
  padding: 12px 22px;
  border-radius: var(--radius-md);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: transform var(--transition-fast), background var(--transition-fast), border-color var(--transition-fast);
}

.btn:hover {
  transform: translateY(-2px);
}

.btn-primary {
  background: var(--amber);
  color: #fff;
  border: 1px solid var(--amber);
}

[data-theme="dark"] .btn-primary {
  color: #0b0d10;
}

.btn-ghost {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text-primary);
}

.btn-ghost:hover {
  border-color: var(--cyan);
  color: var(--cyan);
}

.footer {
  padding: 36px 40px;
  max-width: var(--content-max);
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  font-size: 12px;
  color: var(--text-muted);
  border-top: 1px solid var(--line);
}

@media (max-width: 860px) {
  .rail { display: none; }
  .shell { margin-left: 0; }
  .topnav { left: 0; padding: 0 20px; }
  .nav-links { display: none; }
  section { padding: 80px 20px; }
  .footer { padding: 32px 20px; }
}