:root {
    --bg-gradient: linear-gradient(135deg, #0f172a 0%, #1e1b4b 100%);
    --sidebar-bg: rgba(15, 23, 42, 0.65);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-primary: #8b5cf6;
    --accent-hover: #7c3aed;
    --accent-success: #10b981;
    --accent-success-hover: #059669;
    --item-hover: rgba(139, 92, 246, 0.15);
    --item-active: rgba(139, 92, 246, 0.25);
    --item-active-border: #a78bfa;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg-gradient);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    display: flex;
    height: 100vh;
    width: 100vw;
    padding: 1rem;
    gap: 1rem;
}

/* Glassmorphism Sidebar */
.sidebar {
    width: 350px;
    background: var(--sidebar-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    display: flex;
    flex-direction: column;
    box-shadow: var(--glass-shadow);
    z-index: 10;
    overflow: hidden;
}

.sidebar-header {
    padding: 28px 24px 20px;
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    flex-direction: column;
    gap: 20px;
    background: rgba(255,255,255,0.02);
}

.sidebar-header h2 {
    font-size: 1.5rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 12px;
    color: #fff;
    letter-spacing: -0.03em;
    text-shadow: 0 2px 10px rgba(139, 92, 246, 0.3);
}

.sidebar-header h2 i {
    color: var(--item-active-border);
    filter: drop-shadow(0 0 8px rgba(167, 139, 250, 0.5));
}

.sidebar-actions {
    display: flex;
    gap: 12px;
}

.upload-btn {
    flex: 1;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-hover));
    color: white;
    padding: 12px 16px;
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.95rem;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    border: 1px solid rgba(255,255,255,0.1);
    box-shadow: 0 4px 15px rgba(139, 92, 246, 0.3);
}

.upload-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(139, 92, 246, 0.4);
}

.upload-btn:active {
    transform: translateY(1px);
}

.bulk-save-btn {
    background: linear-gradient(135deg, var(--accent-success), var(--accent-success-hover)) !important;
    box-shadow: 0 4px 15px rgba(16, 185, 129, 0.2) !important;
}

.bulk-save-btn:hover {
    box-shadow: 0 8px 25px rgba(16, 185, 129, 0.3) !important;
}

.bulk-save-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    background: #374151 !important;
    box-shadow: none !important;
    transform: none !important;
    color: #9ca3af;
    border-color: transparent !important;
}

.invoice-list {
    flex: 1;
    overflow-y: auto;
    padding: 16px;
}

.invoice-list::-webkit-scrollbar {
    width: 6px;
}
.invoice-list::-webkit-scrollbar-thumb {
    background-color: rgba(255,255,255,0.1);
    border-radius: 10px;
}

.empty-list-msg {
    color: var(--text-secondary);
    text-align: center;
    padding: 40px 20px;
    font-size: 1rem;
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 15px;
    opacity: 0.7;
}

.empty-list-msg i {
    font-size: 3rem;
    color: rgba(255,255,255,0.1);
}

.invoice-item {
    padding: 16px;
    border-radius: 14px;
    margin-bottom: 10px;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid transparent;
    display: flex;
    flex-direction: column;
    gap: 8px;
    background: rgba(255, 255, 255, 0.03);
    position: relative;
    overflow: hidden;
}

.invoice-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--item-active-border);
    transform: scaleY(0);
    transition: transform 0.3s ease;
    border-radius: 4px 0 0 4px;
}

.invoice-item:hover {
    background: var(--item-hover);
    border-color: rgba(139, 92, 246, 0.3);
    transform: translateX(4px);
}

.invoice-item.active {
    background: var(--item-active);
    border-color: rgba(139, 92, 246, 0.5);
}

.invoice-item.active::before {
    transform: scaleY(1);
}

.invoice-item-title {
    font-size: 1rem;
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    color: #fff;
}

.invoice-item-date {
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 6px;
}

.invoice-item-date i {
    font-size: 0.75rem;
}

/* Main Content Area */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--sidebar-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    box-shadow: var(--glass-shadow);
    overflow: hidden;
    position: relative;
}

.top-bar {
    height: 76px;
    background: rgba(255,255,255,0.02);
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 32px;
    z-index: 2;
}

.top-bar h3 {
    font-size: 1.2rem;
    font-weight: 600;
    color: #fff;
    display: flex;
    align-items: center;
    gap: 10px;
}

.top-bar h3::before {
    content: '';
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--accent-primary);
    box-shadow: 0 0 10px var(--accent-primary);
}

.actions {
    display: flex;
    gap: 12px;
}

.action-btn {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
    border: 1px solid rgba(255,255,255,0.1);
    padding: 10px 18px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all 0.3s ease;
    backdrop-filter: blur(4px);
}

.action-btn:not(:disabled):hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: rgba(255,255,255,0.2);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

.action-btn:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

/* Viewer Container */
.viewer-container {
    flex: 1;
    position: relative;
    padding: 24px;
    display: flex;
    justify-content: center;
    align-items: center;
    background: radial-gradient(circle at center, rgba(139, 92, 246, 0.05) 0%, transparent 70%);
}

.viewer-container.dragover {
    background: rgba(139, 92, 246, 0.1);
}

.viewer-container.dragover::after {
    content: '';
    position: absolute;
    top: 24px;
    left: 24px;
    right: 24px;
    bottom: 24px;
    border: 2px dashed var(--accent-primary);
    border-radius: 16px;
    pointer-events: none;
    z-index: 5;
    animation: pulseBorder 2s infinite;
}

@keyframes pulseBorder {
    0% { border-color: rgba(139, 92, 246, 0.5); }
    50% { border-color: rgba(139, 92, 246, 1); }
    100% { border-color: rgba(139, 92, 246, 0.5); }
}

.drop-message {
    text-align: center;
    color: var(--text-secondary);
    pointer-events: none;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
    background: rgba(15, 23, 42, 0.4);
    padding: 40px 60px;
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(8px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.2);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.viewer-container.dragover .drop-message {
    transform: scale(1.05);
    border-color: rgba(139, 92, 246, 0.4);
    box-shadow: 0 20px 50px rgba(139, 92, 246, 0.2);
}

.drop-message i.main-icon {
    font-size: 5rem;
    background: -webkit-linear-gradient(135deg, #a78bfa, #7c3aed);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    filter: drop-shadow(0 10px 20px rgba(139,92,246,0.3));
    margin-bottom: 10px;
}

.drop-message p {
    font-size: 1.5rem;
    font-weight: 600;
    color: #fff;
    letter-spacing: -0.02em;
}

.drop-message span {
    font-size: 1.05rem;
    color: var(--text-secondary);
    background: rgba(255,255,255,0.05);
    padding: 8px 16px;
    border-radius: 20px;
    border: 1px solid rgba(255,255,255,0.05);
}

#invoice-frame {
    width: 100%;
    height: 100%;
    background-color: #ffffff;
    border: none;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    opacity: 0;
    animation: slideUpFade 0.5s forwards ease-out;
}

@keyframes slideUpFade {
    0% {
        opacity: 0;
        transform: translateY(20px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}