:root { 
    --bg: #0f172a; 
    --card: rgba(255, 255, 255, 0.95); 
    --text: #1e293b; 
    --muted: #64748b; 
    --accent: #2563eb; 
    --border: #e2e8f0;
    --radius: 12px; 
}

* { box-sizing: border-box; }

body { 
    margin: 0; 
    font-family: system-ui, -apple-system, sans-serif; 
    background-color: var(--bg);
    color: var(--text); 
    line-height: 1.5;
    overflow-x: hidden;
}

/* CANVAS BACKGROUND */
#bg-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
}

/* NAVIGATION */
.nav-container { 
    width: 100%; 
    background: #fff; 
    border-bottom: 1px solid var(--border); 
    position: sticky; 
    top: 0; 
    z-index: 1000; 
}
.nav-bar { 
    max-width: 1100px; 
    margin: 0 auto; 
    display: flex; 
    justify-content: flex-end; 
    gap: 20px; 
    padding: 12px 20px; 
}
.nav-link { 
    text-decoration: none; 
    color: var(--muted); 
    font-size: 13px; 
    font-weight: 600; 
    transition: 0.2s; 
}
.nav-link:hover { color: var(--accent); }

/* MAIN CONTAINER */
.container { 
    width: 100%; 
    max-width: 1100px; 
    margin: 40px auto; 
    background: var(--card); 
    border: 1px solid var(--border); 
    border-radius: var(--radius); 
    padding: 25px; 
    box-shadow: 0 20px 40px rgba(0,0,0,0.3); 
    position: relative;
}

header { 
    margin-bottom: 24px; 
    border-left: 4px solid var(--accent); 
    padding-left: 15px; 
}
header h1 { margin: 0; font-size: 28px; color: #0f172a; }

/* VIDEO PLAYER */
.main-video { 
    position: relative; 
    background: #000; 
    border-radius: 12px; 
    overflow: hidden; 
    aspect-ratio: 16/9; 
    margin-bottom: 15px; 
}
.main-video video { width: 100%; height: 100%; display: block; }

.thumbs-grid { 
    display: grid; 
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); 
    gap: 15px; 
    margin-bottom: 30px; 
}
.video-thumb { 
    display: flex; 
    gap: 12px; 
    padding: 12px; 
    background: #fff; 
    border: 1px solid var(--border); 
    border-radius: 12px; 
    cursor: pointer; 
    transition: 0.2s; 
}
.video-thumb.active { border-color: var(--accent); background: #eff6ff; }
.video-thumb img { width: 100px; aspect-ratio: 16/9; border-radius: 6px; object-fit: cover; }

/* CONTENT GRIDS */
.section-title { 
    margin: 40px 0 20px; 
    font-size: 18px; 
    font-weight: 700; 
    border-bottom: 2px solid #f1f5f9; 
    padding-bottom: 8px; 
}
.card-grid { 
    display: grid; 
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); 
    gap: 15px; 
}
.content-card { 
    background: #fff; 
    border: 1px solid var(--border); 
    border-radius: 12px; 
    overflow: hidden; 
    display: flex; 
    flex-direction: column; 
}
.content-card img { width: 100%; aspect-ratio: 16/9; object-fit: cover; }
.content-card .body { padding: 15px; flex-grow: 1; }
.content-card button { 
    background: var(--accent); 
    color: #fff; 
    border: none; 
    width: 100%; 
    padding: 10px; 
    border-radius: 8px; 
    font-weight: 700; 
    cursor: pointer; 
}

/* LECTURE GRID */
.lecture-grid { 
    display: grid; 
    grid-template-columns: 1.5fr 1fr; 
    gap: 20px; 
    margin-bottom: 30px; 
}
.big-lecture { 
    position: relative; 
    border-radius: 12px; 
    overflow: hidden; 
    cursor: pointer; 
    border: 1px solid var(--border); 
}
.big-lecture img { width: 100%; display: block; }
.lecture-overlay { 
    position: absolute; 
    inset: 0; 
    background: rgba(15, 23, 42, 0.7); 
    display: flex; 
    flex-direction: column; 
    align-items: center; 
    justify-content: center; 
    color: #fff; 
}
.small-lecture-list { 
    display: grid; 
    grid-template-columns: 1fr 1fr; 
    gap: 12px; 
}
.lecture-item { 
    border: 1px solid var(--border); 
    border-radius: 10px; 
    overflow: hidden; 
    cursor: pointer; 
    background: #fff; 
}
.lecture-item img { width: 100%; aspect-ratio: 3/2; object-fit: cover; }
.lecture-item .cap { padding: 8px; font-size: 12px; text-align: center; font-weight: 600; }

/* ONE PAGER */
.pdf-box { border-radius: 12px; overflow: hidden; border: 1px solid var(--border); }
.pdf-box iframe { width: 100%; height: 600px; border: none; display: block; }

/* MODAL */
#gateModal { 
    display: none; 
    position: fixed; 
    inset: 0; 
    z-index: 9999; 
    background: rgba(15, 23, 42, 0.6); 
    backdrop-filter: blur(4px); 
    align-items: center; 
    justify-content: center; 
    padding: 20px; 
}
.modal-box { 
    background: #fff; 
    width: 100%; 
    max-width: 500px; 
    border-radius: 16px; 
    padding: 25px; 
}
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.form-group { display: flex; flex-direction: column; margin-bottom: 12px; }
.form-group label { 
    font-size: 11px; 
    font-weight: 700; 
    color: var(--muted); 
    text-transform: uppercase; 
    margin-bottom: 4px; 
}
.form-group input { 
    background: #f8fafc; 
    border: 1px solid var(--border); 
    padding: 10px; 
    border-radius: 6px; 
    font-family: inherit; 
}
.divider { margin: 20px 0; border-top: 2px dashed var(--border); position: relative; }
.divider span { 
    position: absolute; 
    top: -12px; 
    left: 50%; 
    transform: translateX(-50%); 
    background: #fff; 
    padding: 0 10px; 
    font-size: 11px; 
    color: var(--muted); 
    font-weight: 700; 
}

footer { text-align: center; padding: 40px 0; font-size: 12px; color: var(--muted); }

@media (max-width: 800px) { 
    .lecture-grid { grid-template-columns: 1fr; } 
    .form-row { grid-template-columns: 1fr; } 
}