:root {
    --fg: #1a1a1a;
    --muted: #6a6a6a;
    --border: #e2e2e2;
    --bg: #f4f4f5;
    --card: #fff;
    --card-hover: #f7f7f8;
    --footer-bg: #2a4d7a;
    --max: 860px;

    --purple: #6f42c1;
    --indigo: #5b3fd1;
    --blue: #2a6db5;
    --cyan: #1c8ca8;
    --teal: #1a9988;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font:
        16px/1.6 -apple-system,
        "Segoe UI",
        Roboto,
        Helvetica,
        Arial,
        sans-serif;
    color: var(--fg);
    background: var(--bg);
}

a {
    color: inherit;
    text-decoration: none;
}

.wrap {
    max-width: var(--max);
    margin: 0 auto;
    padding: 2.5rem 1.25rem;
}

/* Header + language switcher */
.topbar {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    gap: 1rem;
}
.langs a {
    color: var(--muted);
    font-size: 0.85rem;
    padding: 0 0.35rem;
}
.langs a.active {
    color: var(--fg);
    font-weight: 600;
}
.langs a:hover {
    color: var(--blue);
}

h1 {
    font-size: 1.7rem;
    margin: 0;
}
h2 {
    font-size: 1.35rem;
    margin: 0;
}
h3 {
    font-size: 1.2rem;
    margin: 0;
}
h4 {
    font-size: 1rem;
    margin: 0;
    font-weight: 600;
}

.subtitle {
    color: var(--muted);
    margin: 0.4rem 0 0;
}
.section {
    margin-top: 3rem;
}
.section > .desc {
    color: var(--muted);
    margin: 0.5rem 0 0;
}
.subsection {
    margin-top: 1.5rem;
}

/* Big feature card (Intro, Projects) */
.card {
    display: flex;
    align-items: center;
    gap: 1rem;
    background: var(--card);
    border-radius: 12px;
    padding: 1rem;
    margin-top: 1rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
    transition: background 0.15s;
}
.card:hover {
    background: var(--card-hover);
}
.card .title {
    font-weight: 600;
}
.card .desc {
    font-weight: 400;
    font-size: 0.875rem;
    color: var(--muted);
}

/* Grid of small lesson tiles */
.grid {
    display: grid;
    gap: 0.75rem;
    margin-top: 0.9rem;
    padding: 0.75rem;
    border-radius: 12px;
    background: #e8e8ea;
    grid-template-columns: repeat(3, minmax(0, 1fr));
}
@media (max-width: 640px) {
    .grid {
        grid-template-columns: 1fr;
    }
}

.tile {
    display: flex;
    align-items: center;
    gap: 0.65rem;
    background: var(--card);
    border-radius: 8px;
    padding: 0.55rem;
    transition:
        box-shadow 0.15s,
        background 0.15s;
}
.tile:hover {
    background: var(--card-hover);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.12);
}
.tile .label {
    font-size: 0.9rem;
}

/* Colored icon squares */
.icon {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    color: #fff;
    border-radius: 6px;
}
.icon.sm {
    width: 2rem;
    height: 2rem;
    font-size: 0.95rem;
}
.icon.md {
    width: 2.6rem;
    height: 2.6rem;
    font-size: 1.1rem;
}
.icon.lg {
    width: 3rem;
    height: 3rem;
    font-size: 1.2rem;
}

.bg-purple {
    background: var(--purple);
}
.bg-indigo {
    background: var(--indigo);
}
.bg-blue {
    background: var(--blue);
}
.bg-cyan {
    background: var(--cyan);
}
.bg-teal {
    background: var(--teal);
}

/* Footer */
footer {
    background: var(--footer-bg);
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.8rem;
    margin-top: 3.5rem;
    padding: 1.5rem 0;
}
footer .inner {
    max-width: var(--max);
    margin: 0 auto;
    padding: 0 1.25rem;
}
footer .inner p {
    margin: 0.5rem 0;
}

.badge {
    display: inline-block;
    margin-left: 8px;
    padding: 2px 8px;
    border-radius: 10px;
    background: #e5e7eb;
    color: #4b5563;
    font-size: 11px;
    white-space: nowrap;
    vertical-align: middle;
}

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