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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --error-color: #ef4444;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
}

.screen {
    display: none;
}

.screen.active {
    display: block;
}

/* Login Screen */
.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.login-box {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 400px;
}

.login-box h1 {
    margin-bottom: 2rem;
    text-align: center;
    color: var(--text-primary);
    font-size: 1.75rem;
    font-weight: 600;
}

/* Container */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Cards */
.card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

.card h2 {
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Form */
.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-block;
    text-align: center;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
}

.btn-secondary {
    background: var(--secondary-color);
    color: white;
}

.btn-secondary:hover {
    background: #475569;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Info Box */
.info-box {
    background: #f1f5f9;
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
}

.info-box p {
    margin: 0.5rem 0;
    color: var(--text-secondary);
}

/* Code Display */
.result-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.result-card h2 {
    color: white;
}

.code-display {
    text-align: center;
    margin: 2rem 0;
}

.code-value {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: 0.2em;
    margin-bottom: 1.5rem;
    font-family: 'Courier New', monospace;
    background: rgba(255, 255, 255, 0.2);
    padding: 1rem 2rem;
    border-radius: 8px;
    display: inline-block;
}

.code-info {
    background: rgba(255, 255, 255, 0.1);
    padding: 1.5rem;
    border-radius: 8px;
    margin-top: 1.5rem;
}

.code-info p {
    margin: 0.75rem 0;
    font-size: 1rem;
}

/* Error Message */
.error-message {
    background: #fee2e2;
    color: #991b1b;
    padding: 1rem;
    border-radius: 8px;
    margin: 1rem 0;
    border-left: 4px solid var(--error-color);
}

/* Loading State */
.loading {
    opacity: 0.6;
    pointer-events: none;
}

/* Codes List */
.codes-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.codes-header p {
    font-size: 1.1rem;
    font-weight: 500;
    margin: 0;
}

.codes-actions {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.codes-list {
    max-height: 600px;
    overflow-y: auto;
    margin-top: 1rem;
}

.code-item {
    background: rgba(255, 255, 255, 0.15);
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 0.75rem;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.code-number {
    background: rgba(255, 255, 255, 0.3);
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.code-content {
    flex: 1;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.code-value-small {
    font-family: 'Courier New', monospace;
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: 0.1em;
}

.btn-copy-code {
    padding: 0.5rem 1rem;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 6px;
    color: white;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s;
}

.btn-copy-code:hover {
    background: rgba(255, 255, 255, 0.3);
}

.loading-text {
    text-align: center;
    padding: 2rem;
    font-size: 1.1rem;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    .card {
        padding: 1.5rem;
    }

    header {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }

    .code-value {
        font-size: 1.75rem;
    }

    .codes-header {
        flex-direction: column;
        align-items: stretch;
    }

    .code-content {
        flex-direction: column;
        align-items: stretch;
    }

    .btn-copy-code {
        width: 100%;
    }
}