/* ============================================
   CSS Variables and Theme
   ============================================ */
:root {
    /* Colors */
    --color-primary: #3b82f6;
    --color-primary-dark: #2563eb;
    --color-primary-light: #60a5fa;
    --color-secondary: #6b7280;
    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;
    --color-danger: #dc2626;

    /* Backgrounds */
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --bg-overlay: rgba(0, 0, 0, 0.5);

    /* Text */
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --text-tertiary: #9ca3af;
    --text-inverse: #ffffff;

    /* Borders */
    --border-color: #e5e7eb;
    --border-color-focus: var(--color-primary);
    --border-radius: 0.5rem;
    --border-radius-lg: 0.75rem;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 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);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;

    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;

    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 300ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    min-height: 100vh;
}

/* ============================================
   Accessibility
   ============================================ */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Focus styles for keyboard navigation */
*:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ============================================
   Layout
   ============================================ */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

.main {
    margin-top: var(--spacing-xl);
}

/* ============================================
   Header
   ============================================ */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg);
    background-color: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.header__title {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--text-primary);
}

.header__icon {
    width: 32px;
    height: 32px;
    color: var(--color-primary);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--font-size-base);
    font-weight: 500;
    line-height: 1.5;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.btn__icon {
    width: 20px;
    height: 20px;
}

.btn__spinner {
    width: 16px;
    height: 16px;
    border: 2px solid currentColor;
    border-right-color: transparent;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

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

.btn--primary:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
    box-shadow: var(--shadow-md);
}

.btn--secondary {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn--secondary:hover:not(:disabled) {
    background-color: var(--border-color);
}

.btn--danger {
    background-color: var(--color-danger);
    color: var(--text-inverse);
}

.btn--danger:hover:not(:disabled) {
    background-color: #b91c1c;
    box-shadow: var(--shadow-md);
}

/* ============================================
   Loading State
   ============================================ */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl);
    gap: var(--spacing-md);
}

.loading__spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border-color);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.loading__text {
    color: var(--text-secondary);
    font-size: var(--font-size-lg);
}

/* ============================================
   Alerts
   ============================================ */
.alert {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.alert__icon {
    width: 24px;
    height: 24px;
    flex-shrink: 0;
}

.alert__content {
    flex: 1;
}

.alert__title {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-weight: 600;
}

.alert__message {
    margin: 0;
}

.alert__close {
    background: none;
    border: none;
    padding: 0;
    width: 20px;
    height: 20px;
    cursor: pointer;
    color: currentColor;
    opacity: 0.7;
    transition: opacity var(--transition-fast);
    flex-shrink: 0;
}

.alert__close:hover {
    opacity: 1;
}

.alert__close svg {
    width: 100%;
    height: 100%;
}

.alert--error {
    background-color: #fef2f2;
    color: #991b1b;
    border: 1px solid #fecaca;
}

.alert--success {
    background-color: #f0fdf4;
    color: #166534;
    border: 1px solid #bbf7d0;
}

/* ============================================
   Notes Grid
   ============================================ */
.notes-section {
    background-color: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
}

.notes-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

/* ============================================
   Note Card
   ============================================ */
.note-card {
    background-color: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    transition: all var(--transition-base);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.note-card:hover {
    border-color: var(--color-primary-light);
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.note-card__header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--spacing-sm);
}

.note-card__title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
    word-break: break-word;
    flex: 1;
}

.note-card__actions {
    display: flex;
    gap: var(--spacing-xs);
    flex-shrink: 0;
}

.note-card__btn {
    background: none;
    border: none;
    padding: var(--spacing-xs);
    cursor: pointer;
    color: var(--text-secondary);
    border-radius: var(--border-radius);
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.note-card__btn svg {
    width: 18px;
    height: 18px;
}

.note-card__btn--edit:hover {
    background-color: var(--bg-secondary);
    color: var(--color-primary);
}

.note-card__btn--delete:hover {
    background-color: #fef2f2;
    color: var(--color-danger);
}

.note-card__content {
    color: var(--text-secondary);
    font-size: var(--font-size-base);
    line-height: 1.6;
    display: -webkit-box;
    -webkit-line-clamp: 4;
    -webkit-box-orient: vertical;
    overflow: hidden;
    word-break: break-word;
    white-space: pre-wrap;
}

.note-card__footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-sm);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

.note-card__date {
    font-size: var(--font-size-sm);
    color: var(--text-tertiary);
}

/* ============================================
   Empty State
   ============================================ */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl);
    text-align: center;
}

.empty-state__icon {
    width: 64px;
    height: 64px;
    color: var(--text-tertiary);
    margin-bottom: var(--spacing-lg);
}

.empty-state__title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.empty-state__text {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

/* ============================================
   Form Section
   ============================================ */
.form-section {
    background-color: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
}

.form-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-lg);
    border-bottom: 2px solid var(--border-color);
}

.form-header__title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}

/* ============================================
   Note Form
   ============================================ */
.note-form {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

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

.form-label__required {
    color: var(--color-error);
}

.form-input,
.form-textarea {
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    transition: all var(--transition-fast);
}

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

.form-input::placeholder,
.form-textarea::placeholder {
    color: var(--text-tertiary);
}

.form-input.error,
.form-textarea.error {
    border-color: var(--color-error);
}

.form-input.error:focus,
.form-textarea.error:focus {
    box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.1);
}

.form-textarea {
    resize: vertical;
    min-height: 200px;
}

.form-hint {
    font-size: var(--font-size-sm);
    color: var(--text-tertiary);
}

.form-error {
    font-size: var(--font-size-sm);
    color: var(--color-error);
    font-weight: 500;
    min-height: 1.25rem;
}

.form-actions {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-md);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
}

/* ============================================
   Modal
   ============================================ */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-lg);
}

.modal__backdrop {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--bg-overlay);
    animation: fadeIn var(--transition-base);
}

.modal__content {
    position: relative;
    background-color: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-xl);
    max-width: 500px;
    width: 100%;
    animation: slideUp var(--transition-base);
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

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

.modal__header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
}

.modal__title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin: 0;
}

.modal__close {
    background: none;
    border: none;
    padding: var(--spacing-xs);
    cursor: pointer;
    color: var(--text-secondary);
    border-radius: var(--border-radius);
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal__close:hover {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
}

.modal__close svg {
    width: 20px;
    height: 20px;
}

.modal__body {
    padding: var(--spacing-lg);
}

.modal__body p {
    margin-bottom: var(--spacing-md);
    color: var(--text-secondary);
}

.modal__body p:last-child {
    margin-bottom: 0;
}

.modal__warning {
    font-size: var(--font-size-sm);
    color: var(--color-warning);
    font-weight: 500;
}

.modal__footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }

    .header {
        padding: var(--spacing-md);
    }

    .header__title {
        font-size: var(--font-size-xl);
    }

    .header__icon {
        width: 28px;
        height: 28px;
    }

    .notes-section,
    .form-section {
        padding: var(--spacing-lg);
    }

    .notes-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }

    .form-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-md);
    }

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

    .form-actions .btn {
        width: 100%;
    }

    .modal {
        padding: var(--spacing-md);
    }

    .modal__footer {
        flex-direction: column-reverse;
    }

    .modal__footer .btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    :root {
        --font-size-base: 0.9375rem;
    }

    .container {
        padding: var(--spacing-sm);
    }

    .header {
        flex-direction: column;
        align-items: stretch;
    }

    .btn {
        padding: var(--spacing-sm) var(--spacing-md);
        font-size: var(--font-size-sm);
    }

    .form-textarea {
        min-height: 150px;
    }
}

/* ============================================
   Print Styles
   ============================================ */
@media print {
    .header,
    .btn,
    .note-card__actions,
    .form-section,
    .modal,
    .alert {
        display: none !important;
    }

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

    .note-card {
        page-break-inside: avoid;
        box-shadow: none;
        border: 1px solid #000;
    }
}