/* CSS Variables */
:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #6b7280;
    --secondary-hover: #4b5563;
    --success-color: #10b981;
    --error-color: #ef4444;
    --background: #f8fafc;
    --surface: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px 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);
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --transition: all 0.2s ease;
}

/* Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* Base Styles */
html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Container */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 2rem;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-img {
    width: 48px;
    height: 48px;
    object-fit: contain;
}

h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Main */
main {
    flex: 1;
}

/* Mode Selector */
.mode-selector {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    background: var(--surface);
    padding: 0.25rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.mode-btn {
    flex: 1;
    padding: 0.75rem 1rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius-md);
    transition: var(--transition);
}

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

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

/* Encoding Type */
.encoding-type {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--surface);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.encoding-type label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.95rem;
}

.encoding-type input[type="radio"] {
    width: 18px;
    height: 18px;
    accent-color: var(--primary-color);
}

.radio-label {
    color: var(--text-primary);
    font-weight: 500;
}

.tooltip {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 18px;
    height: 18px;
    background: var(--border-color);
    color: var(--text-secondary);
    border-radius: 50%;
    font-size: 0.75rem;
    cursor: help;
}

/* Panel */
.panel {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    margin-bottom: 2rem;
}

.hidden {
    display: none !important;
}

/* Input/Output Sections */
.input-section,
.output-section {
    margin-bottom: 1rem;
}

.input-section label,
.output-section label {
    display: block;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

textarea {
    width: 100%;
    padding: 0.875rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    font-size: 0.9rem;
    line-height: 1.5;
    resize: vertical;
    transition: var(--transition);
    background: var(--surface);
    color: var(--text-primary);
}

textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

textarea[readonly] {
    background: var(--background);
}

.char-count {
    text-align: right;
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.output-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 0.5rem;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* Buttons */
.action-buttons {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

.btn-icon {
    font-size: 1rem;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

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

.btn-secondary:hover {
    background: var(--secondary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-outline {
    background: transparent;
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
}

.btn-outline:hover {
    border-color: var(--secondary-color);
    color: var(--text-primary);
}

.btn-copy {
    background: var(--success-color);
    color: white;
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
}

.btn-copy:hover:not(:disabled) {
    background: #059669;
    transform: translateY(-1px);
}

.btn-copy:disabled {
    background: var(--border-color);
    color: var(--text-secondary);
    cursor: not-allowed;
}

.copy-icon {
    font-size: 0.9rem;
}

/* Info Section */
.info-section {
    margin-top: 2rem;
}

.info-section h2 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1rem;
}

.info-card {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.info-card h3 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: var(--primary-color);
}

.info-card p,
.info-card li {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.info-card ul {
    list-style: none;
    padding-left: 0;
}

.info-card li {
    padding: 0.25rem 0;
    padding-left: 1.25rem;
    position: relative;
}

.info-card li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--primary-color);
}

.info-card code {
    background: var(--background);
    padding: 0.15rem 0.4rem;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    color: var(--primary-color);
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 0 1rem;
    margin-top: auto;
    border-top: 1px solid var(--border-color);
}

footer p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Toast Notification */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    background: var(--text-primary);
    color: white;
    padding: 0.875rem 1.5rem;
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.toast.show {
    opacity: 1;
    visibility: visible;
}

.toast.success {
    background: var(--success-color);
}

.toast.error {
    background: var(--error-color);
}

/* Responsive Design */
@media (max-width: 640px) {
    .container {
        padding: 1rem;
    }

    h1 {
        font-size: 1.5rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .logo-img {
        width: 36px;
        height: 36px;
    }

    .mode-selector {
        flex-direction: column;
    }

    .encoding-type {
        flex-direction: column;
        gap: 0.75rem;
    }

    .panel {
        padding: 1rem;
    }

    .action-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

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

    textarea {
        font-size: 0.85rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0.75rem;
    }

    h1 {
        font-size: 1.25rem;
    }

    .panel {
        padding: 0.875rem;
    }
}

/* Dark Mode Support */
@media (prefers-color-scheme: dark) {
    :root {
        --background: #0f172a;
        --surface: #1e293b;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --border-color: #334155;
    }

    textarea {
        background: var(--surface);
    }

    textarea[readonly] {
        background: #0f172a;
    }

    .mode-btn:hover {
        background: #334155;
    }

    .tooltip {
        background: #334155;
    }

    .info-card code {
        background: #0f172a;
    }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    * {
        transition: none !important;
    }
}

/* Focus States */
button:focus-visible,
input:focus-visible,
textarea:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}