/* Desktop */
.mobile-break {
    display: none;
}

.desktop-separator {
    display: inline;
}

/* Main Container (Light Mode) */
.banner-container {
    width: 100%;
    max-width: 1200px;
    min-height: 500px;
    background: radial-gradient(circle at 50% 0%, 
        #2a85e8 0%, 
        #0b5394 55%, 
        #052644 100%);
    border-radius: 16px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    color: white;
    font-family: 'Hind Siliguri', Kalpurush, sans-serif;
    position: relative;
    overflow: hidden;
    margin: 0 auto;
    text-align: center;
    border: 1px solid rgba(255,255,255,0.15);
    padding: 40px 20px;
    box-sizing: border-box;
    transition: background 0.3s ease, border-color 0.3s ease;
}

/* Background Symbols */
.bg-symbol {
    position: absolute;
    font-weight: bold;
    font-family: 'Times New Roman', serif;
    pointer-events: none;
}

.symbol-sigma {
    top: 5%;
    left: 6%;
    font-size: clamp(80px, 12vw, 150px);
    color: rgba(255,255,255,0.06);
    transform: rotate(-15deg);
}

.symbol-inf {
    bottom: 5%;
    right: 6%;
    font-size: clamp(100px, 15vw, 180px);
    color: rgba(255,255,255,0.06);
    transform: rotate(10deg);
}

.symbol-pi {
    top: 40%;
    left: -20px;
    font-size: clamp(80px, 11vw, 130px);
    color: rgba(255,255,255,0.04);
}

.symbol-sn {
    bottom: 15%;
    left: 12%;
    font-size: clamp(28px, 4vw, 45px);
    color: rgba(255,255,255,0.05);
    font-style: italic;
}

.symbol-formula {
    top: 18%;
    right: 8%;
    font-size: clamp(22px, 3.5vw, 40px);
    color: rgba(255,255,255,0.05);
    transform: rotate(15deg);
    font-style: italic;
}

/* Chapter Badge */
.chapter-badge {
    background: linear-gradient(90deg, #ffc107 0%, #ff9800 100%);
    color: #000;
    padding: 6px 28px;
    border-radius: 30px;
    font-size: clamp(14px, 2vw, 18px);
    margin-bottom: 20px;
    font-weight: 800;
    letter-spacing: 1.5px;
    box-shadow: 0 4px 15px rgba(255, 152, 0, 0.4);
    z-index: 2;
}

/* Main Title */
.main-title {
    font-size: clamp(42px, 7vw, 90px);
    margin: 0 0 8px 0;
    text-shadow: 0 8px 16px rgba(0,0,0,0.4);
    font-weight: 900;
    letter-spacing: 2px;
    line-height: 1.2;
    z-index: 2;
}

/* Subtitle */
.subtitle {
    font-size: clamp(16px, 2.5vw, 32px);
    margin: 0 0 40px 0;
    font-weight: 500;
    color: #e3f2fd;
    text-shadow: 0 2px 4px rgba(0,0,0,0.3);
    line-height: 1.5;
    z-index: 2;
    transition: color 0.3s ease;
}

.subtitle span {
    color: #ffeb3b;
    font-weight: 700;
}

/* Formula Container & Boxes */
.formula-container {
    display: flex;
    gap: 24px;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    padding: 0 10px;
    z-index: 2;
    width: 100%;
    box-sizing: border-box;
}

.formula-box {
    background: rgba(255, 255, 255, 0.95);
    color: #052644;
    padding: 15px 35px;
    border-radius: 12px;
    font-weight: bold;
    font-size: clamp(17px, 2.5vw, 28px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.25);
    border-bottom: 4px solid #ff9800;
    backdrop-filter: blur(5px);
    max-width: 100%;
    box-sizing: border-box;
    overflow-x: auto;
    transition: background 0.3s ease, color 0.3s ease;
}


/* ===========================
   Dark Mode Overrides
   =========================== */
body.dark-mode .banner-container {
    background: radial-gradient(circle at 50% 0%, #1e293b 0%, #0f172a 55%, #020617 100%) !important;
    border-color: rgba(255, 255, 255, 0.08) !important;
}

body.dark-mode .subtitle {
    color: #94a3b8 !important;
}

body.dark-mode .formula-box {
    background: rgba(15, 23, 42, 0.95) !important;
    color: #f8fafc !important;
}


/* ===========================
   Mobile Responsive
   =========================== */
@media (max-width: 600px) {
    .banner-container {
        min-height: 620px !important;
        padding: 35px 12px !important;
        border-radius: 12px !important;
    }

    .mobile-break {
        display: block;
    }

    .desktop-separator {
        display: none;
    }

    .formula-container {
        flex-direction: column !important;
        gap: 15px !important;
    }

    .formula-box {
        width: 100% !important;
        padding: 13px 12px !important;
        font-size: 18px !important;
    }
}