:root {
    --primary-color: #6366F1;
    --primary-hover: #5558E3;
    --secondary-color: #1DA1F2;
    --success-color: #10B981;
    --error-color: #EF4444;
    --dark-bg: #0F172A;
    --dark-surface: #1E293B;
    --dark-border: #334155;
    --light-bg: #F8FAFC;
    --light-surface: #FFFFFF;
    --light-border: #E2E8F0;
    --text-primary: #1E293B;
    --text-secondary: #64748B;
    --text-light: #94A3B8;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1);
}

[data-theme="dark"] {
    --text-primary: #F1F5F9;
    --text-secondary: #CBD5E1;
    --text-light: #94A3B8;
    --light-bg: #0F172A;
    --light-surface: #1E293B;
    --light-border: #334155;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--light-bg);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* App Container */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
}

/* Professional Header */
.app-header {
    background: var(--light-surface);
    border-bottom: 1px solid var(--light-border);
    box-shadow: var(--shadow-sm);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 100%;
}

.brand {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.logo svg {
    color: var(--primary-color);
}

.logo span {
    font-size: 1.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.brand-tag {
    color: var(--text-secondary);
    font-size: 0.875rem;
    padding: 0.25rem 0.75rem;
    background: var(--light-bg);
    border-radius: 20px;
    border: 1px solid var(--light-border);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.theme-toggle {
    background: var(--light-bg);
    border: 1px solid var(--light-border);
    border-radius: 12px;
    width: 44px;
    height: 44px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    color: var(--text-secondary);
}

.theme-toggle:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

/* Ad Slots */
.ad-slot {
    margin: 1rem 0;
}

.ad-footer {
    padding: 1rem 2rem;
    background: var(--light-surface);
    border-top: 1px solid var(--light-border);
}

.ad-vertical {
    margin-top: 2rem;
}

.ad-placeholder {
    background: linear-gradient(135deg, #F3F4F6 0%, #E5E7EB 100%);
    border: 2px dashed #D1D5DB;
    border-radius: 12px;
    padding: 1rem;
    text-align: center;
    position: relative;
}

[data-theme="dark"] .ad-placeholder {
    background: linear-gradient(135deg, #1F2937 0%, #111827 100%);
    border-color: #374151;
}

.ad-label {
    position: absolute;
    top: 0.5rem;
    left: 0.5rem;
    font-size: 0.75rem;
    color: var(--text-light);
    background: var(--light-surface);
    padding: 0.125rem 0.5rem;
    border-radius: 4px;
}

.ad-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 60px;
    color: var(--text-light);
    font-size: 0.875rem;
}

.ad-footer .ad-content {
    min-height: 90px;
}

.ad-vertical .ad-content {
    min-height: 250px;
}

/* Main Content Layout */
.main-content {
    display: flex;
    flex: 1;
    overflow: hidden;
}

/* Preview Panel (Left) */
.preview-panel {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--light-bg);
    border-right: 1px solid var(--light-border);
    overflow-y: auto;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background: var(--light-surface);
    border-bottom: 1px solid var(--light-border);
}

.panel-header-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.panel-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.preview-status {
    font-size: 0.875rem;
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    background: var(--light-bg);
    border-radius: 20px;
    border: 1px solid var(--light-border);
}

.canvas-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    overflow: hidden;
}

.preview-section {
    width: 100%;
    max-width: 400px;
}

.preview-wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: 0.75rem;
    padding: 25px;
    border-radius: 16px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    transition: background 0.3s ease;
}

.tweet-card {
    width: 100%;
    max-width: 320px;
    height: 320px;
    background: var(--light-surface);
    border: 1px solid var(--light-border);
    border-radius: 20px;
    padding: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    box-shadow: var(--shadow-lg);
    position: relative;
    overflow: hidden;
}

.tweet-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.tweet-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    object-fit: cover;
}

.tweet-user-info {
    flex: 1;
    text-align: left;
}

.tweet-name {
    font-weight: 700;
    color: var(--text-primary);
    font-size: 0.85rem;
    line-height: 1.2;
}

.tweet-username {
    color: var(--text-secondary);
    font-size: 0.75rem;
}

.twitter-logo {
    color: var(--secondary-color);
    width: 20px;
    height: 20px;
}

.tweet-content {
    flex: 1;
    text-align: left;
    font-size: 0.875rem;
    line-height: 1.3;
    color: var(--text-primary);
    overflow: hidden;
    display: -webkit-box;
    -webkit-line-clamp: 6;
    -webkit-box-orient: vertical;
}

.tweet-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 0.5rem;
    border-top: 1px solid var(--light-border);
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.download-info {
    text-align: center;
    margin-top: 0.25rem;
    font-size: 0.7rem;
    color: var(--text-light);
}

.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    color: var(--text-light);
}

.empty-state p {
    font-size: 1.125rem;
}

/* Controls Panel (Right) */
.controls-panel {
    width: 420px;
    background: var(--light-surface);
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}

.control-section {
    padding: 1.5rem;
    border-bottom: 1px solid var(--light-border);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.25rem;
}

.section-header h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.section-icon {
    color: var(--success-color);
}

.section-badge {
    font-size: 0.75rem;
    padding: 0.25rem 0.5rem;
    background: var(--primary-color);
    color: white;
    border-radius: 12px;
    font-weight: 500;
}

/* Input Groups */
.input-group {
    margin-bottom: 1.25rem;
}

.input-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.url-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--light-border);
    border-radius: 10px;
    font-size: 0.9rem;
    transition: all 0.2s ease;
    background: var(--light-bg);
    color: var(--text-primary);
}

.url-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
    background: var(--light-surface);
}

.input-helper {
    display: block;
    font-size: 0.75rem;
    color: var(--text-light);
    margin-top: 0.25rem;
}

/* Buttons */
.primary-btn {
    width: 100%;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-hover) 100%);
    color: white;
    border: none;
    padding: 0.875rem 1.5rem;
    border-radius: 10px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    box-shadow: var(--shadow-md);
}

.primary-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.primary-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.panel-header .download-btn {
    width: auto;
    padding: 0.625rem 1.25rem;
    font-size: 0.9rem;
    background: linear-gradient(135deg, var(--success-color) 0%, #059669 100%);
}

.loading-spinner {
    width: 18px;
    height: 18px;
    border: 2px solid transparent;
    border-top: 2px solid currentColor;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    display: none;
}

.convert-btn.loading .loading-spinner {
    display: block;
}

.convert-btn.loading .btn-text {
    display: none;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Error Message */
.error-message {
    background: #FEF2F2;
    border: 1px solid #FECACA;
    color: var(--error-color);
    padding: 0.75rem 1rem;
    border-radius: 8px;
    font-size: 0.875rem;
    display: none;
    margin-top: 0.75rem;
}

[data-theme="dark"] .error-message {
    background: rgba(239, 68, 68, 0.1);
    border-color: rgba(239, 68, 68, 0.3);
}

.error-message.show {
    display: block;
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Background Selector */
.background-section {
    padding-bottom: 0;
}

.background-selector {
    margin-top: 1rem;
}

.bg-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    background: var(--light-bg);
    padding: 0.25rem;
    border-radius: 10px;
}

.bg-tab {
    flex: 1;
    padding: 0.5rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.bg-tab:hover {
    background: rgba(99, 102, 241, 0.1);
}

.bg-tab.active {
    background: var(--primary-color);
    color: white;
}

.background-options-container {
    margin-bottom: 1rem;
}

.background-options {
    display: none;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.75rem;
}

.background-options.active {
    display: grid;
}

.background-option {
    position: relative;
    cursor: pointer;
    border-radius: 10px;
    overflow: hidden;
    transition: all 0.2s ease;
    border: 3px solid transparent;
    text-align: center;
}

.background-option:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
}

.background-option.active {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.bg-preview {
    width: 100%;
    height: 80px;
    border-radius: 7px;
    position: relative;
}

.bg-label {
    display: block;
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
    font-weight: 500;
}

/* Pattern backgrounds */
.pattern-dots {
    background: #f0f9ff;
    background-image: radial-gradient(circle, rgba(29, 161, 242, 0.2) 2px, transparent 2px);
    background-size: 20px 20px;
}

.pattern-lines {
    background: #f0f9ff;
    background-image: repeating-linear-gradient(
        45deg,
        transparent,
        transparent 10px,
        rgba(29, 161, 242, 0.1) 10px,
        rgba(29, 161, 242, 0.1) 20px
    );
}

.pattern-grid {
    background: #f0f9ff;
    background-image: 
        linear-gradient(rgba(29, 161, 242, 0.1) 1px, transparent 1px),
        linear-gradient(90deg, rgba(29, 161, 242, 0.1) 1px, transparent 1px);
    background-size: 20px 20px;
}

/* Custom color picker */
.custom-color-section {
    padding: 1rem 0;
    border-top: 1px solid var(--light-border);
}

.color-picker-option {
    width: 100px;
    position: relative;
}

.color-picker-option input[type="color"] {
    position: absolute;
    width: 100%;
    height: 80px;
    opacity: 0;
    cursor: pointer;
}

#custom-preview {
    background: linear-gradient(45deg, #ddd 25%, transparent 25%, transparent 75%, #ddd 75%, #ddd),
                linear-gradient(45deg, #ddd 25%, transparent 25%, transparent 75%, #ddd 75%, #ddd);
    background-size: 10px 10px;
    background-position: 0 0, 5px 5px;
}

/* Responsive Design */
@media (max-width: 1200px) {
    .controls-panel {
        width: 380px;
    }
}

@media (max-width: 992px) {
    .main-content {
        flex-direction: column;
    }
    
    .preview-panel {
        border-right: none;
        border-bottom: 1px solid var(--light-border);
        min-height: 400px;
    }
    
    .controls-panel {
        width: 100%;
    }
    
    .ad-vertical {
        display: none;
    }
}

@media (max-width: 768px) {
    .header-content {
        padding: 1rem;
    }
    
    .brand-tag {
        display: none;
    }
    
    .logo span {
        font-size: 1.25rem;
    }
    
    .ad-footer {
        padding: 0.75rem 1rem;
    }
    
    .panel-header {
        padding: 1rem;
    }
    
    .canvas-container {
        padding: 1rem;
    }
    
    .preview-wrapper {
        padding: 20px;
    }
    
    .tweet-card {
        max-width: 280px;
        height: 280px;
    }
    
    .control-section {
        padding: 1rem;
    }
    
    .background-options {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .preview-wrapper {
        padding: 15px;
    }
    
    .tweet-card {
        max-width: 260px;
        height: 260px;
        padding: 1rem;
    }
    
    .tweet-avatar {
        width: 36px;
        height: 36px;
    }
    
    .tweet-content {
        font-size: 0.8rem;
        -webkit-line-clamp: 5;
    }
    
    .panel-header .download-btn {
        padding: 0.5rem 1rem;
        font-size: 0.85rem;
    }
}