```css
/* ==========================================
   DRIN ELECTRONICS ACADEMY
========================================== */

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Segoe UI", sans-serif;
}

body {
    background: #f5f7fb;
    color: #222;
}

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

.academy-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: #00bcd4;
    box-shadow: 0 2px 10px rgba(0, 0, 0, .08);
}

.academy-nav {
    max-width: 1300px;
    margin: auto;
    height: 70px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 25px;
}

.academy-brand {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: #fff;
    font-size: 20px;
    font-weight: bold;
}

.academy-brand img {
    width: 42px;
    height: 42px;
}

.back-home-btn {
    color: #fff;
    text-decoration: none;
    border: 1px solid rgba(255, 255, 255, .35);
    padding: 10px 18px;
    border-radius: 8px;
    transition: .3s;
}

.back-home-btn:hover {
    background: #fff;
    color: #00bcd4;
}

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

.academy-hero {
    background: linear-gradient(135deg, #00bcd4, #0097a7);
    color: #fff;
    text-align: center;
    padding: 70px 20px;
}

.academy-hero h1 {
    font-size: 42px;
    margin: 15px 0;
}

.academy-hero p {
    max-width: 760px;
    margin: auto;
    font-size: 17px;
    line-height: 1.8;
}

.academy-badge {
    display: inline-block;
    background: #fff;
    color: #00bcd4;
    padding: 7px 16px;
    border-radius: 30px;
    font-size: 13px;
    font-weight: bold;
}

/* ===========================
SEARCH
=========================== */

.academy-search-box {
    max-width: 720px;
    margin: 35px auto 0;
    display: flex;
    background: #fff;
    border-radius: 50px;
    overflow: hidden;
    box-shadow: 0 15px 35px rgba(0, 0, 0, .15);
}

.academy-search-box input {
    flex: 1;
    border: none;
    padding: 18px;
    font-size: 15px;
    outline: none;
}

.academy-search-box button {
    border: none;
    background: #0097a7;
    color: #fff;
    padding: 0 30px;
    cursor: pointer;
    font-size: 15px;
}

/* ===========================
CATEGORY
=========================== */

.academy-category-section {
    background: #fff;
    padding: 25px;
}

.academy-category-tabs {
    display: flex;
    gap: 12px;
    overflow-x: auto;
}

.category-tab {
    border: none;
    background: #eceff1;
    padding: 12px 22px;
    border-radius: 30px;
    cursor: pointer;
    white-space: nowrap;
    font-weight: 600;
}

.category-tab.active {
    background: #00bcd4;
    color: #fff;
}

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

.academy-content-section {
    max-width: 1300px;
    margin: auto;
    padding: 50px 20px;
}

.section-heading {
    margin-bottom: 30px;
}

.section-heading h2 {
    font-size: 32px;
}

.section-heading p {
    color: #666;
    margin-top: 8px;
}

/* ===========================
GRID
=========================== */

.academy-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(330px, 1fr));
    gap: 25px;
}

/* ===========================
CARD
=========================== */

.academy-card {
    background: #fff;
    border-radius: 16px;
    padding: 22px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, .08);
    transition: .25s;
}

.academy-card:hover {
    transform: translateY(-5px);
}

.pdf-icon {
    width: 70px;
    height: 70px;
    border-radius: 50%;
    background: #e0f7fa;
    color: #00bcd4;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 32px;
    margin-bottom: 18px;
}

.pdf-category {
    color: #00bcd4;
    font-size: 13px;
    font-weight: bold;
}

.pdf-title {
    font-size: 22px;
    font-weight: bold;
    margin: 12px 0;
}

.pdf-description {
    color: #666;
    line-height: 1.7;
    margin-bottom: 20px;
}

.download-btn {
    display: inline-block;
    text-decoration: none;
    background: #00bcd4;
    color: #fff;
    padding: 12px 20px;
    border-radius: 8px;
    transition: .25s;
}

.download-btn:hover {
    background: #0097a7;
}

/* ===========================
EMPTY
=========================== */

.academy-empty {
    text-align: center;
    padding: 80px;
}

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

.academy-footer {
    background: #111827;
    color: #fff;
    text-align: center;
    padding: 25px;
    margin-top: 50px;
}

/* ===========================
RESPONSIVE
=========================== */

@media(max-width:768px) {

    .academy-nav {
        flex-direction: column;
        height: auto;
        padding: 20px;
        gap: 15px;
    }

    .academy-hero h1 {
        font-size: 32px;
    }

    .academy-search-box {
        flex-direction: column;
        border-radius: 15px;
    }

    .academy-search-box button {
        padding: 15px;
    }

    .section-heading h2 {
        font-size: 26px;
    }

    .academy-grid {
        grid-template-columns: 1fr;
    }

}

/* ===========================
PREMIUM COMING SOON NOTICE
=========================== */

.academy-premium-notice {
    max-width: 1200px;
    margin: 28px auto;
    padding: 22px;
    background: linear-gradient(135deg, #ffffff, #f0fbfd);
    border: 1px solid rgba(0, 188, 212, .22);
    border-radius: 20px;
    display: flex;
    align-items: center;
    gap: 18px;
    box-shadow: 0 14px 35px rgba(0, 0, 0, .08);
}

.notice-icon {
    width: 64px;
    height: 64px;
    border-radius: 18px;
    background: linear-gradient(135deg, #00bcd4, #0097a7);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 30px;
    flex-shrink: 0;
}

.notice-badge {
    display: inline-block;
    margin-bottom: 8px;
    padding: 5px 12px;
    border-radius: 999px;
    background: #fff3cd;
    color: #b45309;
    font-size: 12px;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: .5px;
}

.notice-content h3 {
    font-size: 20px;
    color: #111827;
    margin-bottom: 6px;
}

.notice-content p {
    color: #475569;
    font-size: 14px;
    line-height: 1.7;
}

@media(max-width:768px) {
    .academy-premium-notice {
        margin: 20px 14px;
        align-items: flex-start;
    }

    .notice-icon {
        width: 52px;
        height: 52px;
        font-size: 24px;
    }

    .notice-content h3 {
        font-size: 17px;
    }
}