/* ============================================================
   Design tokens + shared UI — dark (default) & light themes
   Preserves the site's original identity: dark, steel-blue
   accent, glassmorphism cards, subtle glow.
   ============================================================ */

:root {
    /* accent identity (kept from original #607d8b + blue glow) */
    --accent: #5db4ff;
    --accent-strong: #2f8fe6;
    --accent-steel: #607d8b;
    --accent-soft: rgba(93, 180, 255, 0.14);
    --accent-glow: rgba(9, 185, 255, 0.35);

    /* dark theme (default) */
    --bg-color: #0a0e17;
    --bg-image: url(../images/black.jpeg);
    --bg-overlay: linear-gradient(180deg, rgba(6, 10, 20, 0.72), rgba(6, 10, 20, 0.86));

    --text: #e7edf5;
    --text-muted: #9fb0c3;
    --heading: #ffffff;

    --surface: rgba(255, 255, 255, 0.055);
    --surface-2: rgba(255, 255, 255, 0.09);
    --surface-hover: rgba(255, 255, 255, 0.12);
    --border: rgba(255, 255, 255, 0.12);
    --border-strong: rgba(255, 255, 255, 0.2);

    --icon-tile: #f4f7fb;              /* light tile behind logos so dark logos stay visible */
    --icon-tile-border: rgba(255, 255, 255, 0.25);

    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.25);
    --shadow-md: 0 8px 30px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 18px 50px rgba(0, 0, 0, 0.45);
    --glass-blur: blur(8px);

    --radius-sm: 10px;
    --radius: 16px;
    --radius-lg: 22px;

    --maxw: 1100px;
    --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
    --gh-theme: algolia;

    color-scheme: dark;
}

:root[data-theme="light"] {
    --bg-color: #e8eef7;
    --bg-image: none;
    --bg-overlay: radial-gradient(1100px 620px at 88% -8%, rgba(47, 143, 230, 0.22), transparent 58%),
        radial-gradient(900px 560px at -8% 112%, rgba(99, 102, 241, 0.16), transparent 58%),
        radial-gradient(700px 500px at 50% 120%, rgba(45, 212, 191, 0.10), transparent 60%),
        linear-gradient(165deg, #f4f8ff 0%, #e6edf8 55%, #dde7f5 100%);

    --text: #33465c;
    --text-muted: #647588;
    --heading: #0f1c2e;

    --surface: #ffffff;
    --surface-2: #f3f7fd;
    --surface-hover: #ffffff;
    --border: rgba(20, 40, 70, 0.09);
    --border-strong: rgba(20, 40, 70, 0.16);

    --icon-tile: #ffffff;
    --icon-tile-border: rgba(20, 40, 70, 0.08);

    --shadow-sm: 0 4px 14px rgba(30, 55, 95, 0.08);
    --shadow-md: 0 14px 36px rgba(30, 55, 95, 0.12);
    --shadow-lg: 0 26px 60px rgba(30, 55, 95, 0.18);
    --glass-blur: blur(6px);

    --accent: #2f7fe0;
    --accent-strong: #1c62bd;
    --accent-glow: rgba(47, 127, 224, 0.28);
    --accent-soft: rgba(47, 127, 224, 0.10);

    --gh-theme: default;
    color-scheme: light;
}

/* ---------- base ---------- */
* {
    box-sizing: border-box;
}

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

body {
    margin: 0;
    padding: 0;
    font-family: Cambria, Cochin, Georgia, Times, "Times New Roman", serif;
    color: var(--text);
    background-color: var(--bg-color);
    background-image: var(--bg-overlay), var(--bg-image);
    background-size: cover, cover;
    background-position: center;
    background-repeat: no-repeat;
    background-attachment: fixed;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    transition: background-color 0.4s var(--ease), color 0.4s var(--ease);
}

img {
    max-width: 100%;
}

::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-thumb {
    background-color: var(--accent-steel);
    border-radius: 8px;
}

::selection {
    background: var(--accent-soft);
    color: var(--heading);
}

/* ---------- section rhythm & headers ---------- */
.section {
    scroll-margin-top: 80px;
    padding: 56px 0;
}

.section-head {
    text-align: center;
    margin-bottom: 42px;
}

.section-title {
    display: inline-block;
    color: var(--heading);
    font-size: clamp(1.9rem, 4vw, 2.6rem);
    margin: 0;
    letter-spacing: 0.5px;
    position: relative;
    padding-bottom: 14px;
}

.section-title::after {
    content: "";
    position: absolute;
    left: 50%;
    bottom: 0;
    transform: translateX(-50%);
    width: 64px;
    height: 4px;
    border-radius: 4px;
    background: linear-gradient(90deg, var(--accent), var(--accent-steel));
    box-shadow: 0 0 16px var(--accent-glow);
}

.section-subtitle {
    color: var(--text-muted);
    margin: 14px auto 0;
    max-width: 640px;
    font-size: 1.05rem;
    line-height: 1.6;
}

/* ---------- tech tags / chips ---------- */
.tag-row {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    justify-content: center;
    margin-top: 16px;
}

.tag {
    font-size: 0.82rem;
    letter-spacing: 0.3px;
    padding: 5px 12px;
    border-radius: 999px;
    color: var(--text);
    background: var(--surface-2);
    border: 1px solid var(--border);
    transition: border-color 0.25s, transform 0.25s, background 0.25s;
}

.tag:hover {
    border-color: var(--accent);
    background: var(--accent-soft);
    transform: translateY(-2px);
}

/* ---------- buttons ---------- */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 0.7rem 1.4rem;
    border-radius: 999px;
    font-size: 0.98rem;
    font-weight: 600;
    letter-spacing: 0.4px;
    cursor: pointer;
    text-decoration: none;
    border: 1px solid transparent;
    transition: transform 0.25s var(--ease), box-shadow 0.25s var(--ease), background 0.25s, color 0.25s;
}

.btn-primary {
    color: #fff;
    background: linear-gradient(120deg, var(--accent-strong), var(--accent));
    box-shadow: 0 8px 22px var(--accent-glow);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 14px 30px var(--accent-glow);
}

.btn-ghost {
    color: var(--text);
    background: var(--surface);
    border-color: var(--border-strong);
}

.btn-ghost:hover {
    transform: translateY(-3px);
    border-color: var(--accent);
    color: var(--accent);
    box-shadow: var(--shadow-sm);
}

.btn:active {
    transform: translateY(-1px);
}

/* ---------- theme toggle ---------- */
.theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    color: var(--text);
    background: var(--surface-2);
    border: 1px solid var(--border-strong);
    transition: transform 0.3s var(--ease), color 0.25s, border-color 0.25s, background 0.25s;
}

.theme-toggle:hover {
    transform: rotate(18deg) scale(1.06);
    color: var(--accent);
    border-color: var(--accent);
}

.theme-toggle svg {
    width: 20px;
    height: 20px;
}

.theme-toggle .icon-sun {
    display: none;
}

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

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

/* ---------- scroll progress bar ---------- */
#scroll-progress {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    width: 0%;
    z-index: 2000;
    background: linear-gradient(90deg, var(--accent-strong), var(--accent), #22d3ee);
    box-shadow: 0 0 12px var(--accent-glow);
    transition: width 0.08s linear;
}

/* ---------- scroll reveal (bolder + replays on scroll) ---------- */
.reveal {
    opacity: 0;
    transform: translateY(46px) scale(0.98);
    transition: opacity 0.7s var(--ease), transform 0.7s var(--ease);
    will-change: opacity, transform;
}

.reveal.is-visible {
    opacity: 1;
    transform: none;
}

/* directional variants */
.reveal-left { transform: translateX(-56px); }
.reveal-right { transform: translateX(56px); }
.reveal-scale { transform: scale(0.86); }
.reveal-left.is-visible,
.reveal-right.is-visible,
.reveal-scale.is-visible { transform: none; }

/* staggered reveal for grids of siblings */
.stagger > .reveal:nth-child(1) { transition-delay: 0.04s; }
.stagger > .reveal:nth-child(2) { transition-delay: 0.10s; }
.stagger > .reveal:nth-child(3) { transition-delay: 0.16s; }
.stagger > .reveal:nth-child(4) { transition-delay: 0.22s; }
.stagger > .reveal:nth-child(5) { transition-delay: 0.28s; }
.stagger > .reveal:nth-child(6) { transition-delay: 0.34s; }
.stagger > .reveal:nth-child(7) { transition-delay: 0.40s; }
.stagger > .reveal:nth-child(8) { transition-delay: 0.46s; }
.stagger > .reveal:nth-child(n+9) { transition-delay: 0.5s; }

/* shine sweep on primary buttons */
.btn-primary {
    position: relative;
    overflow: hidden;
}

.btn-primary::after {
    content: "";
    position: absolute;
    top: 0;
    left: -120%;
    width: 60%;
    height: 100%;
    background: linear-gradient(120deg, transparent, rgba(255, 255, 255, 0.45), transparent);
    transform: skewX(-18deg);
    transition: left 0.6s var(--ease);
}

.btn-primary:hover::after {
    left: 140%;
}

@keyframes fade-up {
    from { opacity: 0; transform: translateY(18px); }
    to { opacity: 1; transform: none; }
}

@keyframes pop-in {
    0% { opacity: 0; transform: scale(0.9); }
    100% { opacity: 1; transform: scale(1); }
}

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.001ms !important;
        transition-duration: 0.001ms !important;
        scroll-behavior: auto !important;
    }

    .reveal {
        opacity: 1;
        transform: none;
    }
}