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

:root {
    --primary-color: #4f46e5;
    --primary-dark: #4338ca;
    --secondary-color: #6366f1;
    --success-color: #10b981;
    --text-color: #1f2937;
    --text-light: #6b7280;
    --border-color: #e5e7eb;
    --bg-color: #f9fafb;
    --white: #ffffff;
    --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);
}

[data-theme="dark"] {
    --text-color: #f3f4f6;
    --text-light: #e5e7eb;
    --border-color: #4b5563;
    --bg-color: #1f2937;
    --white: #111827;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.5), 0 1px 2px 0 rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -2px rgba(0, 0, 0, 0.4);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    padding: 20px;
    transition: background 0.3s ease, color 0.3s ease;
}

[data-theme="dark"] body {
    background: linear-gradient(135deg, #1e1b4b 0%, #312e81 100%);
}

.container {
    max-width: 1000px;
    margin: 0 auto;
}

header {
    margin-bottom: 30px;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: var(--white);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    text-align: left;
}

.theme-toggle {
    background: rgba(255, 255, 255, 0.2);
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: var(--white);
    border-radius: 50%;
    width: 50px;
    height: 50px;
    font-size: 1.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: rotate(15deg);
}

@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: 15px;
    }
    
    header h1 {
        text-align: center;
    }
}

.subtitle {
    font-size: 1.1rem;
    opacity: 0.95;
}

.invoice-form {
    background: var(--white);
    border-radius: 12px;
    padding: 40px;
    box-shadow: var(--shadow-lg);
}

.form-section {
    margin-bottom: 35px;
    padding-bottom: 30px;
    border-bottom: 1px solid var(--border-color);
}

.form-section:last-of-type {
    border-bottom: none;
}

.form-section h2 {
    font-size: 1.5rem;
    color: var(--text-color);
    margin-bottom: 20px;
    font-weight: 600;
}

.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 20px;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group label {
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--text-color);
    font-size: 0.9rem;
}

.form-group input,
.form-group textarea,
.form-group select {
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.2s;
    font-family: inherit;
    background-color: var(--white);
    color: var(--text-color);
}

[data-theme="dark"] .form-group input,
[data-theme="dark"] .form-group textarea,
[data-theme="dark"] .form-group select {
    background-color: #1f2937;
    border-color: #4b5563;
    color: #f3f4f6;
}

[data-theme="dark"] .form-group input::placeholder,
[data-theme="dark"] .form-group textarea::placeholder {
    color: #9ca3af;
    opacity: 0.7;
}

.form-group select {
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23333' d='M6 9L1 4h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 40px;
}

[data-theme="dark"] .form-group select {
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23f3f4f6' d='M6 9L1 4h10z'/%3E%3C/svg%3E");
}

.logo-upload-container {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.logo-input {
    display: none;
}

.logo-upload-btn {
    padding: 10px 20px;
    background: var(--bg-color);
    border: 2px dashed var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    text-align: center;
    transition: all 0.2s;
    color: var(--text-color);
    font-weight: 500;
}

.logo-upload-btn:hover {
    border-color: var(--primary-color);
    background: rgba(79, 70, 229, 0.05);
}

[data-theme="dark"] .logo-upload-btn:hover {
    background: rgba(99, 102, 241, 0.2);
    border-color: #6366f1;
}

.logo-preview {
    max-width: 200px;
    max-height: 100px;
    margin-top: 10px;
}

.logo-preview img {
    max-width: 100%;
    max-height: 100px;
    object-fit: contain;
    border-radius: 8px;
    border: 2px solid var(--border-color);
}

.logo-remove {
    padding: 8px 16px;
    background: #ef4444;
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.9rem;
    width: fit-content;
    transition: all 0.2s;
}

.logo-remove:hover {
    background: #dc2626;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

[data-theme="dark"] .form-group input:focus,
[data-theme="dark"] .form-group textarea:focus,
[data-theme="dark"] .form-group select:focus {
    border-color: #6366f1;
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.3);
}

.form-group textarea {
    resize: vertical;
    min-height: 60px;
}

.item-row {
    display: grid;
    grid-template-columns: 2fr 100px 120px 120px 50px;
    gap: 15px;
    align-items: end;
    margin-bottom: 15px;
    padding: 15px;
    background: var(--bg-color);
    border-radius: 8px;
}

[data-theme="dark"] .item-row {
    background: #374151;
    border: 1px solid #4b5563;
}

.item-description {
    grid-column: 1;
}

.item-quantity {
    grid-column: 2;
}

.item-rate {
    grid-column: 3;
}

.item-total {
    grid-column: 4;
}

.item-actions {
    grid-column: 5;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn-remove {
    background: #ef4444;
    color: white;
    border: none;
    border-radius: 50%;
    width: 30px;
    height: 30px;
    cursor: pointer;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.btn-remove:hover {
    background: #dc2626;
    transform: scale(1.1);
}

.item-total-display {
    background: var(--white);
    font-weight: 600;
    color: var(--primary-color);
}

[data-theme="dark"] .item-total-display {
    background-color: #1f2937;
    color: #818cf8;
}

.totals-section {
    background: var(--bg-color);
    padding: 20px;
    border-radius: 8px;
    margin: 30px 0;
}

[data-theme="dark"] .totals-section {
    background: #374151;
    border: 1px solid #4b5563;
}

.total-row {
    display: flex;
    justify-content: space-between;
    padding: 10px 0;
    font-size: 1rem;
}

.total-row span:first-child {
    color: var(--text-light);
}

.total-row span:last-child {
    font-weight: 600;
    color: var(--text-color);
}

.total-final {
    border-top: 2px solid var(--border-color);
    margin-top: 10px;
    padding-top: 15px;
    font-size: 1.3rem;
}

.total-final span:last-child {
    color: var(--primary-color);
    font-size: 1.5rem;
}

.form-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
    margin-top: 30px;
}

.btn-primary,
.btn-secondary {
    padding: 14px 28px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    font-family: inherit;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: var(--white);
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

[data-theme="dark"] .btn-secondary {
    background: #374151;
    color: #818cf8;
    border-color: #6366f1;
}

[data-theme="dark"] .btn-secondary:hover {
    background: #6366f1;
    color: #ffffff;
}

@media (max-width: 768px) {
    .invoice-form {
        padding: 20px;
    }

    header h1 {
        font-size: 2rem;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    .item-row {
        grid-template-columns: 1fr;
        gap: 10px;
    }

    .item-description,
    .item-quantity,
    .item-rate,
    .item-total,
    .item-actions {
        grid-column: 1;
    }

    .form-actions {
        flex-direction: column;
    }

    .btn-primary,
    .btn-secondary {
        width: 100%;
    }
}