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

body {
    font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: #333;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background-color: #ffffff;
    border-radius: 16px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    max-width: 450px;
    width: 100%;
    padding: 40px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.container::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, #667eea, #764ba2);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5em;
    color: #2d3748;
    font-weight: 700;
}

header p {
    font-size: 1.1rem;
    margin-bottom: 2em;
    color: #718096;
}

#language-selector {
    margin-bottom: 2em;
}

#language-selector label {
    font-weight: 600;
    color: #4a5568;
    margin-right: 10px;
}

#language-selector select {
    padding: 8px 12px;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    font-size: 0.9rem;
    background-color: #f7fafc;
}

.login-card {
    background-color: #f8fafc;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    border: 1px solid #e2e8f0;
}

.login-card h2 {
    margin-bottom: 25px;
    color: #2d3748;
    font-weight: 600;
}

.form-group {
    margin-bottom: 20px;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #4a5568;
    font-size: 0.95rem;
}

.form-group input {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
    background-color: #ffffff;
}

.form-group input:focus {
    border-color: #667eea;
    outline: none;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.login-btn {
    width: 100%;
    padding: 14px;
    background: linear-gradient(135deg, #667eea, #764ba2);
    border: none;
    border-radius: 8px;
    color: white;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 10px;
}

.login-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(102, 126, 234, 0.3);
}

.gamification {
    margin-top: 25px;
    font-size: 1rem;
    color: #718096;
    background-color: #f0f4f8;
    padding: 15px;
    border-radius: 8px;
    border-left: 4px solid #667eea;
}

.progress-bar {
    background-color: #e2e8f0;
    border-radius: 20px;
    height: 8px;
    width: 100%;
    margin: 15px 0;
    overflow: hidden;
}

.progress {
    background: linear-gradient(90deg, #667eea, #764ba2);
    height: 100%;
    width: 0%;
    border-radius: 20px;
    transition: width 0.5s ease-in-out;
}

#message {
    font-style: italic;
    margin-top: 10px;
    color: #4a5568;
    font-size: 0.9rem;
}

.signup-link {
    margin-top: 20px;
    font-size: 0.9rem;
    color: #718096;
}

.signup-link a {
    color: #667eea;
    text-decoration: none;
    font-weight: 600;
}

.signup-link a:hover {
    text-decoration: underline;
}

footer {
    margin-top: 30px;
    font-size: 0.9rem;
    color: #a0aec0;
    font-style: italic;
}

.tab-buttons {
    display: flex;
    justify-content: center;
    margin-bottom: 25px;
    background-color: #edf2f7;
    border-radius: 25px;
    padding: 5px;
}

.tab-btn {
    background-color: transparent;
    border: none;
    padding: 12px 24px;
    margin: 0;
    border-radius: 20px;
    color: #718096;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    flex: 1;
}

.tab-btn.active {
    background-color: #ffffff;
    color: #2d3748;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.tab-btn:hover {
    color: #2d3748;
}

.form-section {
    display: block;
}

.form-section.hidden {
    display: none;
}