:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary-color: #64748b;
    --accent-color: #10b981;
    --accent-dark: #0da26d;
    --danger-color: #ef4444;
    --danger-dark: #dc2626;
    --warning-color: #f59e0b;
    --dark-color: #1e293b;
    --light-color: #f8fafc;
    --border-color: #e2e8f0;
    --header-bg: #f1f5f9;
    --cell-bg: #ffffff;
    --hover-color: #f1f5f9;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 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: 10px;
    --radius-lg: 16px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

body {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    color: #334155;
    height: 100vh;
    overflow: hidden;
}

.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

.app-header {
    background: linear-gradient(135deg, #1e3a8a, #3b82f6);
    color: white;
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
    z-index: 100;
}

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

.logo i {
    font-size: 1.75rem;
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.1));
}

.logo h1 {
    font-size: 1.5rem;
    font-weight: 600;
    background: linear-gradient(135deg, #fff, #bfdbfe);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.current-file {
    background-color: rgba(255, 255, 255, 0.15);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
    backdrop-filter: blur(10px);
}

.current-file:hover {
    background-color: rgba(255, 255, 255, 0.25);
    transform: translateY(-1px);
}

.toolbar {
    background-color: white;
    padding: 0.75rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    box-shadow: var(--shadow-sm);
}

.toolbar-group {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    padding-right: 0.75rem;
    border-right: 1px solid var(--border-color);
}

.toolbar-group:last-child {
    border-right: none;
}

.btn {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: var(--radius-sm);
    background-color: white;
    color: var(--dark-color);
    cursor: pointer;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s ease;
    border: 1px solid transparent;
}

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

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-dark), #1e40af);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-success {
    background: linear-gradient(135deg, var(--accent-color), var(--accent-dark));
    color: white;
    border: none;
}

.btn-success:hover {
    background: linear-gradient(135deg, var(--accent-dark), #0b8a5c);
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger-color), var(--danger-dark));
    color: white;
    border: none;
}

.btn-danger:hover {
    background: linear-gradient(135deg, var(--danger-dark), #b91c1c);
    box-shadow: 0 4px 12px rgba(239, 68, 68, 0.3);
}

.btn-warning {
    background: linear-gradient(135deg, var(--warning-color), #d97706);
    color: white;
    border: none;
}

.btn-warning:hover {
    background: linear-gradient(135deg, #d97706, #b45309);
    box-shadow: 0 4px 12px rgba(245, 158, 11, 0.3);
}

.btn-icon {
    padding: 0.5rem;
    width: 2.25rem;
    justify-content: center;
}

.formula-bar {
    display: flex;
    align-items: center;
    background-color: white;
    padding: 0.5rem 1rem;
    border-bottom: 1px solid var(--border-color);
    gap: 0.5rem;
}

.formula-label {
    font-weight: 600;
    min-width: 60px;
    color: var(--dark-color);
    background-color: var(--header-bg);
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    text-align: center;
}

.formula-input {
    flex: 1;
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-family: 'Consolas', monospace;
    font-size: 0.95rem;
    transition: all 0.2s;
}

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

.fx-icon {
    background-color: var(--primary-color);
    color: white;
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.fx-icon:hover {
    background-color: var(--primary-dark);
    transform: scale(1.05);
}

.range-status {
    background-color: #fef3c7;
    color: #92400e;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.7; }
}

.cancel-range {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    padding: 0 0.25rem;
    color: #92400e;
}

.cancel-range:hover {
    color: #dc2626;
}

.formulas-panel {
    background-color: white;
    border-bottom: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    align-items: center;
}

.formula-btn {
    padding: 0.35rem 0.85rem;
    background: linear-gradient(135deg, #f8fafc, #f1f5f9);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s;
    font-family: 'Consolas', monospace;
}

.formula-btn:hover {
    background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-1px);
}

.spreadsheet-container {
    flex: 1;
    overflow: auto;
    position: relative;
    background-color: #e2e8f0;
    border-radius: var(--radius);
    margin: 1rem;
    box-shadow: var(--shadow-lg);
}

.cell-reference {
    position: absolute;
    top: 0;
    left: 0;
    background: linear-gradient(135deg, var(--header-bg), #e2e8f0);
    z-index: 5;
    padding: 0.5rem;
    font-weight: 600;
    border-right: 1px solid var(--border-color);
    border-bottom: 1px solid var(--border-color);
    min-width: 60px;
    text-align: center;
    border-radius: var(--radius-sm) 0 0 0;
    font-size: 0.85rem;
    color: var(--primary-color);
}

.spreadsheet {
    border-collapse: collapse;
    table-layout: fixed;
    min-width: 100%;
    background-color: white;
    margin-top: 2.5rem;
    margin-left: 3.5rem;
    border-radius: var(--radius);
}

.spreadsheet th {
    background: linear-gradient(135deg, var(--header-bg), #e8edf5);
    border: 1px solid var(--border-color);
    padding: 0.5rem;
    text-align: center;
    font-weight: 600;
    position: sticky;
    top: 0;
    z-index: 10;
    min-width: 100px;
    height: 32px;
    user-select: none;
    font-size: 0.85rem;
    color: var(--dark-color);
}

.spreadsheet td {
    border: 1px solid var(--border-color);
    padding: 0;
    min-width: 100px;
    height: 28px;
    vertical-align: middle;
    position: relative;
    transition: background-color 0.1s;
}

.spreadsheet td:hover {
    background-color: rgba(37, 99, 235, 0.05);
}

.cell-input {
    width: 100%;
    height: 100%;
    border: none;
    padding: 0.25rem 0.5rem;
    font-size: 0.9rem;
    background-color: transparent;
    outline: none;
    cursor: pointer;
}

.cell-input:focus {
    background-color: rgba(37, 99, 235, 0.08);
}

.cell-input.range-selecting {
    cursor: crosshair !important;
}

.row-number {
    position: sticky;
    left: 0;
    background: linear-gradient(135deg, var(--header-bg), #e8edf5);
    border: 1px solid var(--border-color);
    text-align: center;
    font-weight: 600;
    min-width: 3rem;
    z-index: 9;
    user-select: none;
    font-size: 0.85rem;
    color: var(--dark-color);
}

.selected {
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.15), rgba(59, 130, 246, 0.1));
    border: 2px solid var(--primary-color) !important;
    position: relative;
}

.range-highlight {
    background-color: rgba(37, 99, 235, 0.2);
    border: 2px dashed var(--primary-color);
}

.status-bar {
    background-color: white;
    padding: 0.5rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
}

.status-info {
    display: flex;
    gap: 1.5rem;
}

.status-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal-content {
    background-color: white;
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    width: 90%;
    max-width: 500px;
    box-shadow: var(--shadow-lg);
    animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.modal-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--dark-color);
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #64748b;
    transition: all 0.2s;
}

.modal-close:hover {
    color: var(--danger-color);
    transform: scale(1.1);
}

.form-group {
    margin-bottom: 1rem;
}

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

.form-control {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 1rem;
    transition: all 0.2s;
}

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

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
    margin-top: 1.5rem;
}

.context-menu {
    position: absolute;
    background-color: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    display: none;
    flex-direction: column;
    min-width: 200px;
    overflow: hidden;
    animation: contextFadeIn 0.15s ease;
}

@keyframes contextFadeIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.context-menu-item {
    padding: 0.75rem 1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    transition: all 0.2s;
    font-size: 0.9rem;
}

.context-menu-item:hover {
    background: linear-gradient(135deg, var(--hover-color), #e2e8f0);
}

.context-menu-item i {
    width: 20px;
    color: var(--secondary-color);
}

.spreadsheet-container::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

.spreadsheet-container::-webkit-scrollbar-track {
    background: var(--header-bg);
    border-radius: 10px;
}

.spreadsheet-container::-webkit-scrollbar-thumb {
    background: var(--secondary-color);
    border-radius: 10px;
}

.spreadsheet-container::-webkit-scrollbar-thumb:hover {
    background: var(--dark-color);
}

@media (max-width: 1024px) {
    .spreadsheet th, .spreadsheet td {
        min-width: 80px;
    }
}

@media (max-width: 768px) {
    .toolbar {
        padding: 0.5rem;
    }
    
    .btn span {
        display: none;
    }
    
    .btn-icon {
        width: auto;
    }
    
    .spreadsheet {
        margin-left: 2.5rem;
    }
    
    .row-number {
        min-width: 2.5rem;
    }

    .formulas-panel {
        overflow-x: auto;
        flex-wrap: nowrap;
    }
}