:root {
    --primary-color: #007bff;
    --primary-color-hover: #005ec4;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --bg-color: #f8f9fa;
    --card-bg: #ffffff;
    --text-main: #343a40;
    --text-muted: #6c757d;
    --border-color: #dee2e6;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 450px;
    text-align: center;
}

header {
    margin-bottom: 30px;
}

.badge {
    display: inline-block;
    background-color: #e2e3e5;
    color: var(--text-muted);
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    padding: 4px 10px;
    border-radius: 20px;
    letter-spacing: 0.5px;
    margin-bottom: 10px;
}

h1 {
    font-size: 28px;
    font-weight: 700;
    color: #000;
    margin-bottom: 5px;
}

.subtitle {
    font-size: 14px;
    color: var(--text-muted);
}

.card {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 30px;
    box-shadow: var(--shadow);
    text-align: left;
}

.input-group {
    margin-bottom: 25px;
}

.input-group label {
    display: block;
    font-weight: 600;
    font-size: 14px;
    margin-bottom: 10px;
    color: var(--text-muted);
}

.input-group input {
    width: 100%;
    padding: 15px;
    font-size: 20px;
    font-weight: 700;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    outline: none;
    transition: border-color 0.2s;
    letter-spacing: 2px;
    text-transform: uppercase;
    text-align: center;
}

.input-group input:focus {
    border-color: var(--primary-color);
}

.result-area {
    margin-top: 25px;
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    transition: all 0.3s;
}

.result-area.correct {
    background-color: #d4edda;
    border: 1px solid #c3e6cb;
    color: #155724;
}

.result-area.incorrect {
    background-color: #f8d7da;
    border: 1px solid #f5c6cb;
    color: #721c24;
}

.result-area.suggestion-mode {
    background-color: #e7f3ff;
    border: 1px solid #b8daff;
    color: #004085;
}

.hidden {
    display: none;
}

.status-icon {
    font-size: 32px;
    margin-bottom: 10px;
}

.message {
    font-weight: 700;
    font-size: 16px;
    margin-bottom: 5px;
}

.suggestion {
    font-size: 14px;
    opacity: 0.9;
}

.algorithm-brief {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.algorithm-brief h3 {
    font-size: 12px;
    text-transform: uppercase;
    color: var(--text-muted);
    letter-spacing: 1px;
    margin-bottom: 12px;
}

.algorithm-brief ul {
    list-style: none;
    display: flex;
    justify-content: space-between;
}

.algorithm-brief li {
    font-size: 11px;
    color: var(--text-muted);
}

.algorithm-brief li strong {
    color: var(--text-main);
}

.read-article-button {
    display: inline-block;
    margin-top: 20px;
    padding: 10px 16px;
    border-radius: 10px;
    background-color: var(--primary-color);
    color: #fff;
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    transition: background-color 0.2s ease;
}

.read-article-button:hover {
    background-color: var(--primary-color-hover);
}

footer {
    margin-top: 30px;
}

footer p {
    font-size: 12px;
    color: var(--text-muted);
}

@media (max-width: 480px) {
    .card {
        padding: 20px;
    }
}