/* ===================================================== */
/* GLOBAL PAGE DESIGN */
/* ===================================================== */
body {
    margin: 0;
    font-family: "Inter", Arial, sans-serif;
    background: #f4f7fc;
    color: #1f2b45;
    overflow-x: hidden;
}

/* ===================================================== */
/* SIDEBAR */
/* ===================================================== */
.sidebar {
    width: 260px;
    background: #ffffff;
    border-right: 1px solid #e5e8f2;
    height: 100vh;
    position: fixed;
    top: 0;
    left: 0;

    padding: 22px;
    overflow-y: auto;

    border-radius: 0 18px 18px 0;
    box-shadow: 0 5px 25px rgba(0,0,0,0.06);

    transform: translateX(0);
    transition: transform .35s cubic-bezier(0.22, 1, 0.36, 1), opacity .25s ease;

    z-index: 999;
}

.sidebar h2 {
    font-size: 22px;
    font-weight: 900;
    margin-bottom: 18px;
    color: #0d1a3a;
}

/* ===================================================== */
/* CHAPTER MENU STYLING (ADDED AS REQUESTED) */
/* ===================================================== */
.chapter-menu {
    padding: 5px 0;
    padding-bottom: 40px;
}

.chapter-menu a {
    display: flex;
    align-items: center;
    gap: 12px;
    background: #ffffff;
    padding: 12px 14px;
    margin-bottom: 10px;
    border-radius: 12px;
    border: 1px solid #e4e9f2;
    text-decoration: none;
    color: #1f2b45;
    font-size: 15px;
    font-weight: 600;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    transition: all .25s ease;
    position: relative;
}

.chapter-menu a i {
    font-size: 18px;
    color: #0d6efd;
    transition: .3s ease;
}

.chapter-menu a::before {
    content: "";
    position: absolute;
    left: 0;
    top: 10px;
    bottom: 10px;
    width: 4px;
    background: transparent;
    border-radius: 20px;
    transition: .3s ease;
}

.chapter-menu a:hover {
    background: #f4f7ff;
    border-color: #d6e2ff;
    transform: translateX(4px);
    box-shadow: 0 6px 14px rgba(0,0,0,0.08);
}
.chapter-menu a:hover i {
    color: #084fc7;
}

.chapter-menu a.active {
    background: #e7edff;
    border-color: #0d6efd;
    color: #0d3d91;
    box-shadow: 0 6px 16px rgba(13,110,253,0.20);
}
.chapter-menu a.active::before {
    background: #0d6efd;
}
.chapter-menu a.active i {
    color: #0d6efd;
}

@media(max-width: 768px){
    .chapter-menu a {
        padding: 15px 18px;
        font-size: 16px;
        margin-bottom: 12px;
    }
    .chapter-menu {
        padding-bottom: 60px;
    }
}

/* ===================================================== */
/* OVERLAY */
/* ===================================================== */
.overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,.45);
    opacity: 0;
    pointer-events: none;
    transition: opacity .3s ease;
    z-index: 900;
}
.overlay.active {
    opacity: 1;
    pointer-events: all;
}

/* ===================================================== */
/* HAMBURGER */
/* ===================================================== */
.hamburger {
    position: fixed;
    top: 18px;
    left: 16px;
    width: 34px;
    height: 28px;
    cursor: pointer;
    z-index: 1100;
    display: none;
    transition: left .35s cubic-bezier(0.22,1,0.36,1);
}

.hamburger span {
    position: absolute;
    width: 34px;
    height: 4px;
    background: #0d6efd;
    border-radius: 4px;
    transition: all .35s ease;
}

.hamburger span:nth-child(1) { top: 0; }
.hamburger span:nth-child(2) { top: 12px; }
.hamburger span:nth-child(3) { bottom: 0; }

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg);
    top: 12px;
}
.hamburger.active span:nth-child(2) { opacity: 0; }
.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg);
    bottom: 12px;
}

.hamburger.move-right { left: 220px; }

/* ===================================================== */
/* MAIN CONTENT */
/* ===================================================== */
.content {
    margin-left: 300px;
    padding: 45px;
    max-width: 900px;
}

/* ===================================================== */
/* TITLES / HEADINGS */
/* ===================================================== */
.section-title {
    font-size: 34px;
    font-weight: 900;
    color: #0d1a3a;
    margin-bottom: 15px;
}

/* HIGHLIGHT BOX */
.highlight-box {
    background: linear-gradient(135deg, #e6efff, #f5fbff);
    border-left: 6px solid #0d6efd;
    padding: 18px 20px;
    border-radius: 14px;
    margin-bottom: 28px;
    box-shadow: 0 4px 12px rgba(13,110,253,0.15);
}

/* SUB HEADINGS */
.sub-heading {
    font-size: 22px;
    font-weight: 800;
    color: #0d1a3a;
    margin-top: 40px;
    margin-bottom: 12px;
}

/* LIST */
.color-list li {
    margin-bottom: 10px;
    font-size: 16px;
}
.color-list li::marker { color: #0d6efd; }

/* DARK CODE BOX */
.code-box {
    background: #1b2435;
    color: #dce6ff;
    padding: 18px;
    border-radius: 14px;
    font-size: 15px;
    line-height: 1.7;
    border: 1px solid #283144;
    box-shadow: 0 8px 25px rgba(0,0,0,0.45);
    margin: 16px 0 26px;
}

/* DIVIDER */
.section-divider {
    height: 2px;
    margin: 40px 0;
    background: linear-gradient(to right, #0d6efd, #20c997);
    border-radius: 20px;
}

/* TASK BOX */
.task-box {
    background: #e9fff3;
    border-left: 6px solid #20c997;
    padding: 16px 20px;
    border-radius: 14px;
    margin-bottom: 18px;
    box-shadow: 0 4px 12px rgba(32,201,151,0.15);
}

.question-list li::marker { color: #20c997; }

/* ===================================================== */
/* MOBILE */
/* ===================================================== */
@media(max-width:768px){

    .hamburger { display:block; }

    .sidebar {
        transform: translateX(-100%);
        opacity: 0;
        visibility: hidden;
    }

    .sidebar.active {
        transform: translateX(0);
        opacity: 1;
        visibility: visible;
    }

    .content {
        margin-left: 0;
        padding: 100px 22px;
    }
}