/* =====================================
   RESET
===================================== */

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

html{
    scroll-behavior:smooth;
}

body{

    font-family:
    "Segoe UI",
    Arial,
    sans-serif;

    background:#f8fafc;
    color:#1e293b;

    line-height:1.8;
}

/* =====================================
   HEADER
===================================== */

.lesson-header{

    position:sticky;
    top:0;
    z-index:1000;

    display:flex;
    justify-content:space-between;
    align-items:center;
    gap:12px;

    background:#ffffff;

    padding:12px 18px;

    border-bottom:1px solid #e5e7eb;

    box-shadow:
    0 2px 8px rgba(0,0,0,0.05);
}

.logo{

    display:flex;

    align-items:center;
}

.logo img{

    height:46px;

    width:auto;

    display:block;
}

.resource-toggle{

    border:none;

    background:#eef2ff;
    color:#4338ca;

    padding:10px 16px;

    border-radius:10px;

    font-weight:600;

    cursor:pointer;

    white-space:nowrap;
}

/* =====================================
   RESOURCE MENU
===================================== */

.resource-menu{

    display:none;

    background:#ffffff;

    border-bottom:1px solid #e5e7eb;
}

.resource-menu.active{

    display:block;
}

.resource-menu a{

    display:block;

    padding:16px 20px;

    color:#334155;

    text-decoration:none;

    font-weight:600;

    border-bottom:1px solid #f1f5f9;
}

.resource-menu a:hover{

    background:#f8fafc;
}

.resource-menu a.active{

    background:#eef2ff;
    color:#4338ca;

    border-left:4px solid #4338ca;
}

/* =====================================
   HERO
===================================== */

.question-hero{

    text-align:center;

    padding:32px 18px 20px;
}

.reading-time{

    color:#64748b;

    font-size:0.95rem;

    margin-bottom:10px;
}

.question-hero h1{

    font-size:clamp(
        1.6rem,
        5vw,
        2.25rem
    );

    line-height:1.3;

    color:#0f172a;
}

/* =====================================
   CONTENT CARDS
===================================== */

.mq-section{

    background:#ffffff;

    margin:16px;

    padding:18px;

    border-radius:16px;

    box-shadow:
    0 4px 12px rgba(0,0,0,0.05);

    overflow-wrap:break-word;
}

.mq-section h2{

    margin-bottom:12px;

    color:#0f172a;

    font-size:1.2rem;
}

.mq-section p{

    margin-bottom:12px;
}

.mq-section p:last-child{

    margin-bottom:0;
}

.mq-section ul{

    padding-left:22px;
}

.mq-section li{

    margin-bottom:8px;
}

.mq-section img{

    display:block;

    width:100%;
    height:auto;

    border-radius:12px;
}

/* =====================================
   EQUATION
===================================== */

.equation{

    text-align:center;

    font-size:clamp(
        1.15rem,
        4vw,
        1.45rem
    );

    font-weight:700;

    margin:16px 0;

    color:#4338ca;
}

/* =====================================
   MISCONCEPTION BOXES
===================================== */

.misconception{

    background:#fef2f2;

    border-left:4px solid #ef4444;

    padding:14px;

    border-radius:10px;

    margin-bottom:12px;
}

.correct-concept{

    background:#ecfdf5;

    border-left:4px solid #10b981;

    padding:14px;

    border-radius:10px;
}

/* =====================================
   RELATED LINKS
===================================== */

.related-list{

    padding-left:20px;
}

.related-list a{

    color:#4338ca;

    text-decoration:none;
}

.related-list a:hover{

    text-decoration:underline;
}

/* =====================================
   CONTINUE LEARNING
===================================== */

.continue-learning{

    padding:0 16px 24px;
}

.continue-btn{

    display:block;

    text-align:center;

    text-decoration:none;

    background:#4338ca;

    color:#ffffff;

    padding:14px 18px;

    border-radius:12px;

    font-weight:600;

    transition:0.2s;
}

.continue-btn:hover{

    opacity:0.92;
}

/* =====================================
   FOOTER
===================================== */

.site-footer{

    background:#111827;

    color:#ffffff;

    text-align:center;

    padding:24px 16px;
}

/* =====================================
   DESKTOP
===================================== */

@media (min-width:900px){

    .question-hero,
    .continue-learning{

        max-width:900px;

        margin-left:auto;
        margin-right:auto;
    }

    .mq-section{

        max-width:900px;

        margin:20px auto;

        padding:24px;
    }
}
/* =====================================
   LEARNING HUB
===================================== */

.learning-hub{

    padding:0 20px 35px;

    max-width:1100px;

    margin:0 auto;
}

.hub-grid{

    display:grid;

    grid-template-columns:
        repeat(auto-fit,minmax(220px,1fr));

    gap:16px;
}

.hub-card{

    display:block;

    background:#ffffff;

    border:1px solid #e5e7eb;

    border-radius:18px;

    padding:22px;

    text-decoration:none;

    color:inherit;

    transition:0.25s ease;

    box-shadow:
    0 4px 12px rgba(0,0,0,0.05);
}

.hub-card:hover{

    transform:translateY(-3px);

    box-shadow:
    0 8px 20px rgba(0,0,0,0.08);
}

.hub-card h3{

    color:#0f172a;

    margin-bottom:8px;

    font-size:1.05rem;

    font-weight:600;
}

.hub-card p{

    color:#64748b;

    font-size:0.92rem;

    line-height:1.6;
}

/* =====================================
   DESKTOP TUNING
===================================== */

@media (min-width:900px){

    .hub-grid{

        grid-template-columns:
            repeat(3,1fr);
    }

}