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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
}

.screen {
    min-height: 100vh;
}

.hidden {
    display: none !important;
}

/* Login Screen */
.login-form {
    background: white;
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    text-align: center;
    max-width: 400px;
    margin: 100px auto;
}

.login-form h1 {
    margin-bottom: 30px;
    color: #2c3e50;
}

.login-form input {
    width: 100%;
    padding: 12px;
    margin-bottom: 20px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}

.login-form button {
    width: 100%;
    padding: 12px;
    background: #3498db;
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 16px;
    cursor: pointer;
}

.login-form button:hover {
    background: #2980b9;
}

.error {
    color: #e74c3c;
    margin-top: 10px;
    font-size: 14px;
}

/* Classification Screen */
.header {
    background: white;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

.header h1 {
    color: #2c3e50;
    margin: 0;
}

.progress {
    text-align: center;
    flex-grow: 1;
    margin: 0 20px;
}

.progress span {
    font-weight: bold;
    color: #34495e;
}

.email-notice {
    background: #2ecc71;
    color: white;
    padding: 10px;
    border-radius: 4px;
    margin-top: 10px;
    font-weight: bold;
}

.logout-btn {
    padding: 8px 16px;
    background: #95a5a6;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

.logout-btn:hover {
    background: #7f8c8d;
}

/* Article Content */
.article-content {
    background: white;
    padding: 30px;
    border-radius: 8px;
    margin-bottom: 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.article-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.article-header h2 {
    color: #2c3e50;
    flex: 1;
    margin-right: 20px;
    margin-bottom: 10px;
}

.doi-btn {
    padding: 8px 16px;
    background: #e67e22;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    white-space: nowrap;
}

.doi-btn:hover {
    background: #d35400;
}

.abstract {
    margin-top: 20px;
}

.abstract h3 {
    color: #34495e;
    margin-bottom: 10px;
}

.abstract p {
    text-align: justify;
    line-height: 1.8;
}

/* Classification Form */
.classification-form {
    background: white;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

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

.form-group label {
    display: block;
    margin-bottom: 12px;
    font-weight: bold;
    color: #34495e;
    font-size: 16px;
}

.form-group label .help-text {
    font-weight: normal;
    font-size: 14px;
    color: #7f8c8d;
    font-style: italic;
}

.form-group select,
.form-group input {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}

.form-group select:focus,
.form-group input:focus {
    outline: none;
    border-color: #3498db;
    box-shadow: 0 0 5px rgba(52, 152, 219, 0.3);
}

/* Button Groups */
.button-group {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.option-btn {
    padding: 8px 16px;
    border: 2px solid #bdc3c7;
    border-radius: 6px;
    background: white;
    color: #34495e;
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    flex: 0 1 auto;
}

.option-btn:hover {
    border-color: #95a5a6;
    background: #f8f9fa;
}

.option-btn.active {
    background: #3498db;
    border-color: #3498db;
    color: white;
    font-weight: 600;
}

.option-btn.active:hover {
    background: #2980b9;
    border-color: #2980b9;
}

.form-actions {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}

.form-actions button {
    flex: 1;
    padding: 15px;
    border: none;
    border-radius: 4px;
    font-size: 16px;
    cursor: pointer;
    font-weight: bold;
}

.form-actions button:disabled {
    background: #bdc3c7;
    cursor: not-allowed;
}

#prev-btn {
    background: #95a5a6;
    color: white;
}

#prev-btn:not(:disabled):hover {
    background: #7f8c8d;
}

#submit-btn {
    background: #27ae60;
    color: white;
}

#submit-btn:not(:disabled):hover {
    background: #229954;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }

    .header {
        flex-direction: column;
        text-align: center;
    }

    .header h1 {
        margin-bottom: 10px;
    }

    .progress {
        margin: 10px 0;
    }

    .logout-btn {
        margin-top: 10px;
    }

    .article-header {
        flex-direction: column;
    }

    .article-header h2 {
        margin-right: 0;
        margin-bottom: 15px;
    }

    .doi-btn {
        align-self: flex-start;
    }

    .form-actions {
        flex-direction: column;
    }

    .login-form {
        margin: 50px auto;
        padding: 30px;
    }
}

@media (max-width: 768px) {
    .option-btn {
        font-size: 14px;
        padding: 7px 14px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 10px;
    }

    .article-content,
    .classification-form,
    .header {
        padding: 20px;
    }

    .login-form {
        padding: 20px;
        margin: 30px auto;
    }

    .option-btn {
        font-size: 13px;
        padding: 6px 12px;
        flex: 1 1 100%;
    }

    .button-group {
        gap: 8px;
    }
}