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

:root {
    --bg: #f8f7f4;
    --surface: #ffffff;
    --border: #e4e0d8;
    --text: #1c1c1c;
    --muted: #6b6b6b;
    --accent: #2563eb;
    --accent-dim: #dbeafe;
    --radius: 8px;
    --nav-h: 60px;
}

html { scroll-behavior: smooth; }

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

/* ── i18n toggle ── */
.t-es { display: none; }
body.es .t-en { display: none; }
body.es .t-es { display: revert; }

.btn-lang {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--muted);
    font-size: 0.78rem;
    font-weight: 600;
    padding: 0.25rem 0.6rem;
    border-radius: var(--radius);
    cursor: pointer;
    letter-spacing: 0.04em;
    transition: color 0.2s, border-color 0.2s;
}
.btn-lang:hover { color: var(--text); border-color: var(--accent); }

/* ── Navigation ── */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    height: var(--nav-h);
    background: rgba(248, 247, 244, 0.9);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0 2.5rem;
}

#lang-toggle {
    position: absolute;
    right: 2.5rem;
}

nav .logo {
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--text);
    text-decoration: none;
    letter-spacing: -0.02em;
}

nav ul {
    list-style: none;
    display: flex;
    gap: 2rem;
}

nav ul a {
    text-decoration: none;
    color: var(--muted);
    font-size: 0.9rem;
    transition: color 0.2s;
}

nav ul a:hover,
nav ul a.active {
    color: var(--text);
}

nav ul a.active {
    color: var(--accent);
}

/* ── Page wrapper ── */
main {
    padding-top: calc(var(--nav-h) + 3rem);
    padding-bottom: 5rem;
    max-width: 860px;
    margin: 0 auto;
    padding-left: 2rem;
    padding-right: 2rem;
}

/* ── Typography ── */
h1 {
    font-size: 2.8rem;
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.1;
    margin-bottom: 1rem;
}

h2 {
    font-size: 1.4rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--muted);
    margin-bottom: 2.5rem;
}

h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.4rem;
}

p {
    color: var(--muted);
    font-size: 0.95rem;
}

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

a:hover { text-decoration: underline; }

/* ── Section label ── */
.section-label {
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 0.75rem;
}

/* ── Project cards ── */
.cards {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
    margin-top: 1rem;
}

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.4rem 1.6rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    transition: border-color 0.2s;
}

/* ── Flip variant ── */
.card-flip {
    perspective: 1000px;
    background: transparent;
    border: none;
    padding: 0;
}

.card-inner {
    display: grid;
    grid-template-areas: "face";
    transform-style: preserve-3d;
}

.card-front,
.card-back {
    grid-area: face;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    border-radius: var(--radius);
    padding: 1.4rem 1.6rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.card-front {
    background: var(--surface);
    border: 1px solid var(--border);
}

.card-back {
    transform: rotateY(180deg);
    background: var(--accent-dim);
    border: 1px solid var(--accent);
}

.card-why {
    font-size: 0.82rem;
    color: var(--accent);
    font-style: italic;
    border-left: 2px solid var(--accent);
    padding-left: 0.6rem;
    margin-bottom: 0.25rem;
}

.card-meta {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-top: 0.5rem;
    flex-wrap: wrap;
}

.tag {
    font-size: 0.72rem;
    font-weight: 600;
    padding: 0.2rem 0.55rem;
    border-radius: 999px;
    background: var(--accent-dim);
    color: var(--accent);
}

.tag.nb {
    background: #ede9fe;
    color: #6d28d9;
}

.card-links {
    display: flex;
    gap: 1rem;
    margin-top: auto;
    padding-top: 0.5rem;
}

.card-links a {
    font-size: 0.82rem;
    color: var(--muted);
    display: flex;
    align-items: center;
    gap: 0.3rem;
}

.card-links a:hover { color: var(--accent); text-decoration: none; }

/* ── Hero (home) ── */
.hero {
    padding-top: 3rem;
}

.hero .subtitle {
    font-size: 1.1rem;
    color: var(--muted);
    max-width: 520px;
    margin-bottom: 2rem;
}

.hero-links {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.btn {
    display: inline-block;
    padding: 0.55rem 1.2rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    font-weight: 500;
    transition: opacity 0.2s;
}

.btn:hover { opacity: 0.8; text-decoration: none; }

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

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

/* ── Divider ── */
.divider {
    border: none;
    border-top: 1px solid var(--border);
    margin: 3rem 0;
}

/* ── Empty state ── */
.empty {
    padding: 4rem 0;
    color: var(--muted);
    font-size: 0.9rem;
}

/* ── Footer ── */
footer {
    text-align: center;
    padding: 2rem;
    font-size: 0.8rem;
    color: var(--muted);
    border-top: 1px solid var(--border);
}

@media (max-width: 640px) {
    h1 { font-size: 2rem; }
    h2 { font-size: 1.15rem; }

    nav { padding: 0 1rem; }
    nav ul { gap: 1rem; }
    nav ul a { font-size: 0.8rem; }
    #lang-toggle { right: 1rem; }

    main {
        padding-top: calc(var(--nav-h) + 2rem);
        padding-left: 1.25rem;
        padding-right: 1.25rem;
    }

    .hero { padding-top: 1rem; }
    .hero .subtitle { font-size: 0.95rem; }

    .card { padding: 1rem 1.2rem; }
    .divider { margin: 2rem 0; }
}

@media (max-width: 400px) {
    h1 { font-size: 1.6rem; }
    nav ul { gap: 0.6rem; }
    nav ul a { font-size: 0.72rem; }
}