body{
    font-family: system-ui;
    background-color: #33203b;
    color: white;
    margin: 0px;
    display: flex;
    flex-direction: column;
    justify-content: center;  /* vertical centering */
    align-items: center;      /* horizontal centering */
    text-align: center;
    position: relative;       /* make sure ::before sits behind content */
}

body::before {
    content: "";
    position: absolute;
    inset: 0;
    background-image: url('images/math.jpg');
    background-size: cover;
    background-position: center;

    filter: brightness(0.5) blur(2px);  
    z-index: -1;

    position: fixed;
    inset: 0;

}

hr {
    width: 80%;
    border: 1px solid rgb(244, 201, 60);  
}

h2 {
    color: rgb(255, 209, 58);
    font-size: 36px;
}
strong {
    color: rgb(255, 209, 58);
}
.column {
    list-style-type: none;
    text-align: center;
    color: rgb(255, 255, 255);
    
}


li a{
    text-decoration: none;
    color: rgb(18, 66, 169);
}

li a:hover {
    color: yellow;
}
.pdfs {
    column-count: 2;     /* makes two columns */
}

.pdfs li {
    display: block;      /* must be block for column layout */
}

iframe {
    border: none;
    border-radius: 14px;
}

p {
    max-width: 400px;
    color: white;
}

/* 3 column grid layout */
.section-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 25px;
    width: 100%;
    max-width: 1100px;
}

/* boxes inside each column */
.box {
    background-color: rgba(255, 255, 255, 0.35);
    padding: 22px;
    border-radius: 14px;
    backdrop-filter: blur(6px);
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center; /* centers vertically */
    align-items: center;     /* centers horizontally */

}

/* collapse to 1 column on smaller screens */
@media (max-width: 900px) {
    .section-grid {
        grid-template-columns: 1fr;
    }
}

/* PDF links stay in 2 small columns */
.pdfs {
    list-style: none;
    padding: 0;
    column-count: 2;
    column-gap: 15px;
}

.pdfs li {
    padding: 5px 0;
}

/* Demo button */
.demo-link {
    color: rgb(18, 66, 169);
    text-decoration: none;
    font-weight: bold;
}

.demo-link:hover {
    color: yellow;
}

.demo-preview-wrap {
    position: relative;
    width: 100%;
    max-width: 260px;
    height: 160px;
    border-radius: 12px;
    overflow: hidden;
    margin-top: 12px;
}

.demo-preview {
    width: 100%;
    height: 100%;
    border: none;
    border-radius: 12px;
}

/* Dark overlay */
.demo-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0); /* invisible initially */
    transition: background 0.2s ease;
    pointer-events: none; /* ensures clicks still go to the iframe */
}

/* On hover, fade in darkness */
.demo-preview-wrap:hover .demo-overlay {
    background: rgba(0, 0, 0, 0.35);
}

a{
    color: rgb(136, 235, 42);
    text-decoration: none;;
}

a:hover {
    color: rgb(255, 213, 0);
}

.paragraph {
    width: 900px;
}