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

body {
    font-family: Arial, Helvetica, sans-serif;
    background: #07111f;
    color: #ffffff;
    min-height: 100vh;
}

button {
    font: inherit;
    cursor: pointer;
}

.app {
    min-height: 100vh;
}

.screen {
    display: none;
    min-height: 100vh;
    padding: 35px 70px;
}

.screen.active {
    display: block;
}

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 25px;
    font-weight: 700;
}

.logo span {
    color: #63d7ff;
}

.profile,
.progress {
    color: #9caec3;
}

.back {
    background: transparent;
    border: none;
    color: #9caec3;
}

.hero {
    max-width: 850px;
    margin-top: 120px;
}

.eyebrow {
    color: #63d7ff;
    font-size: 14px;
    font-weight: 700;
    letter-spacing: 2px;
    margin-bottom: 18px;
}

h1 {
    font-size: 65px;
    line-height: 1.05;
    margin-bottom: 25px;
}

h2 {
    font-size: 42px;
    margin-bottom: 35px;
}

.description {
    color: #aebdce;
    font-size: 21px;
    line-height: 1.6;
    max-width: 650px;
    margin-bottom: 35px;
}

.primary {
    background: #63d7ff;
    border: none;
    border-radius: 10px;
    padding: 17px 28px;
    color: #04101c;
    font-weight: 700;
    font-size: 17px;
}

.primary:hover {
    transform: translateY(-2px);
}

.features {
    display: flex;
    gap: 25px;
    margin-top: 100px;
}

.features div {
    width: 260px;
    padding: 22px;
    border: 1px solid #23364d;
    border-radius: 12px;
    background: #0c1929;
}

.features strong,
.features span {
    display: block;
}

.features span {
    margin-top: 8px;
    color: #8ea1b6;
}

.content {
    max-width: 1000px;
    margin: 90px auto 0;
}

.topics {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 18px;
    margin-bottom: 35px;
}

.topic {
    text-align: left;
    padding: 25px;
    border-radius: 12px;
    border: 2px solid #243950;
    background: #0c1929;
    color: white;
}

.topic.selected {
    border-color: #63d7ff;
}

.topic b,
.topic span {
    display: block;
}

.topic b {
    font-size: 20px;
    margin-bottom: 8px;
}

.topic span {
    color: #8fa2b7;
}

.ai-card {
    background: #0c1929;
    border: 1px solid #2b4058;
    border-radius: 14px;
    padding: 30px;
    margin-bottom: 25px;
}

.ai-label {
    color: #63d7ff;
    font-weight: 700;
    margin-bottom: 20px;
}

.ai-card p {
    font-size: 21px;
    line-height: 1.7;
    color: #d6e0eb;
}

.lesson-points {
    display: flex;
    gap: 15px;
    margin-bottom: 35px;
}

.lesson-points div {
    flex: 1;
    padding: 18px;
    border-radius: 10px;
    background: #0c1929;
}

.lesson-points strong {
    display: block;
    color: #63d7ff;
    margin-bottom: 8px;
}

.lesson-points span {
    color: #a8b8c9;
}

.answers {
    display: grid;
    gap: 14px;
}

.answers button {
    text-align: left;
    padding: 20px;
    border-radius: 10px;
    border: 1px solid #30465e;
    background: #0c1929;
    color: white;
}

.answers button:hover {
    border-color: #63d7ff;
}

#quizResult {
    margin-top: 25px;
    font-size: 18px;
    color: #63d7ff;
}

.progress-card {
    background: #0c1929;
    border: 1px solid #2b4058;
    border-radius: 15px;
    padding: 35px;
    margin-bottom: 30px;
}

.score strong {
    display: block;
    font-size: 55px;
}

.score span {
    color: #94a7bb;
}

.bar {
    width: 100%;
    height: 12px;
    background: #203147;
    border-radius: 20px;
    margin: 30px 0;
}

.bar-fill {
    width: 67%;
    height: 100%;
    background: #63d7ff;
    border-radius: 20px;
}

.stats {
    display: flex;
    gap: 60px;
}

.stats b,
.stats span {
    display: block;
}

.stats b {
    font-size: 25px;
}

.stats span {
    color: #91a4b8;
    margin-top: 5px;
}

@media (max-width: 800px) {

    .screen {
        padding: 25px;
    }

    h1 {
        font-size: 42px;
    }

    h2 {
        font-size: 32px;
    }

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

    .features,
    .lesson-points {
        flex-direction: column;
    }

    .features div {
        width: 100%;
    }

    .stats {
        gap: 25px;
    }
}