/* 
   PROPIEDADES PERSONALIZADAS CSS (Tokens de Diseño)
    */
:root {
    /* Paleta de Colores */
    --color-primary: #6366f1;
    --color-primary-dark: #4f46e5;
    --color-primary-light: #818cf8;
    --color-secondary: #8b5cf6;
    --color-success: #10b981;
    --color-danger: #ef4444;
    --color-warning: #f59e0b;

    /* Colores Neutrales */
    --color-bg-primary: #0f172a;
    --color-bg-secondary: #1e293b;
    --color-bg-tertiary: #334155;
    --color-surface: #1e293b;
    --color-surface-hover: #334155;

    /* Colores de Texto */
    --color-text-primary: #f1f5f9;
    --color-text-secondary: #cbd5e1;
    --color-text-tertiary: #94a3b8;
    --color-text-muted: #64748b;

    /* Colores de Borde */
    --color-border: #334155;
    --color-border-light: #475569;

    /* Escala de Espaciado (base 4px) */
    --space-1: 0.25rem;
    /* 4px */
    --space-2: 0.5rem;
    /* 8px */
    --space-3: 0.75rem;
    /* 12px */
    --space-4: 1rem;
    /* 16px */
    --space-5: 1.25rem;
    /* 20px */
    --space-6: 1.5rem;
    /* 24px */
    --space-8: 2rem;
    /* 32px */
    --space-10: 2.5rem;
    /* 40px */
    --space-12: 3rem;
    /* 48px */

    /* Tipografía */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-xs: 0.75rem;
    /* 12px */
    --font-size-sm: 0.875rem;
    /* 14px */
    --font-size-base: 1rem;
    /* 16px */
    --font-size-lg: 1.125rem;
    /* 18px */
    --font-size-xl: 1.25rem;
    /* 20px */
    --font-size-2xl: 1.5rem;
    /* 24px */
    --font-size-3xl: 1.875rem;
    /* 30px */

    /* Pesos de Fuente */
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;

    /* Radio de Borde */
    --radius-sm: 0.375rem;
    /* 6px */
    --radius-md: 0.5rem;
    /* 8px */
    --radius-lg: 0.75rem;
    /* 12px */
    --radius-xl: 1rem;
    /* 16px */
    --radius-full: 9999px;

    /* Sombras */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 10px 10px -5px rgba(0, 0, 0, 0.3);

    /* Transiciones */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 200ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 300ms cubic-bezier(0.4, 0, 0.2, 1);

    /* Escala de Z-index */
    --z-base: 1;
    --z-dropdown: 10;
    --z-modal: 100;
    --z-toast: 1000;
}

/* 
   RESET Y ESTILOS BASE
    */
*,
*::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);
    font-weight: var(--font-weight-normal);
    line-height: 1.6;
    color: var(--color-text-primary);
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Oculto Visualmente (solo para lectores de pantalla) */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Estilos de Foco Visible para Accesibilidad */
*:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    border-radius: var(--radius-sm);
}

/* 
   CONTENEDOR DE LA APLICACIÓN
    */
.app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    gap: var(--space-6);
    padding: var(--space-4);
}

/* 
   SIDEBAR (Panel Izquierdo)
    */
.sidebar {
    display: flex;
    flex-direction: column;
    gap: var(--space-6);
}

/* 
   MAIN CONTENT (Panel Derecho)
    */
.main-content {
    flex: 1;
    min-width: 0;
}

/* 
   ENCABEZADO
    */
.app-header {
    animation: slideDown var(--transition-slow) ease-out;
    margin-bottom: var(--space-4);
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.app-title {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-size: var(--font-size-2xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-text-primary);
    padding: var(--space-4);
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(12px);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
}

.app-icon {
    color: var(--color-primary);
    filter: drop-shadow(0 0 8px rgba(99, 102, 241, 0.5));
}

/* 
   CONTENIDO PRINCIPAL
    */
/* Removido - ahora usamos .sidebar y .main-content */

/* 
   FORMULARIO DE TAREAS
    */
.task-form-section {
    animation: fadeIn var(--transition-slow) ease-out 0.1s backwards;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.task-form {
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(12px);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--space-6);
    box-shadow: var(--shadow-md);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.form-label {
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-secondary);
}

.task-input {
    width: 100%;
    padding: var(--space-4);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    color: var(--color-text-primary);
    background: rgba(51, 65, 85, 0.5);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
}

.task-input::placeholder {
    color: var(--color-text-muted);
}

.task-input:hover {
    border-color: var(--color-border-light);
}

.task-input:focus {
    outline: none;
    border-color: var(--color-primary);
    background: rgba(51, 65, 85, 0.7);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

/* Textarea de Descripción */
.task-description-input {
    width: 100%;
    padding: var(--space-3);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    line-height: 1.5;
    color: var(--color-text-primary);
    background: rgba(51, 65, 85, 0.5);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    resize: vertical;
    min-height: 80px;
    transition: all var(--transition-base);
}

.task-description-input::placeholder {
    color: var(--color-text-muted);
}

.task-description-input:hover {
    border-color: var(--color-border-light);
}

.task-description-input:focus {
    outline: none;
    border-color: var(--color-primary);
    background: rgba(51, 65, 85, 0.7);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.form-hint {
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
}

/* 
   BOTONES
    */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-4) var(--space-6);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    line-height: 1;
    text-decoration: none;
    border: none;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-base);
    white-space: nowrap;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary {
    color: white;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    box-shadow: var(--shadow-sm);
}

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

.form-row {
    display: flex;
    gap: var(--space-4);
    align-items: flex-end;
}

.date-group {
    flex: 1;
    min-width: 140px;
}

/* Input de fecha personalizado */
.task-date-input {
    width: 100%;
    padding: var(--space-3);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    color: var(--color-text-primary);
    background: rgba(51, 65, 85, 0.5);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
    cursor: pointer;
}

.task-date-input::-webkit-calendar-picker-indicator {
    filter: invert(1);
    opacity: 0.6;
    cursor: pointer;
    transition: opacity var(--transition-fast);
}

.task-date-input::-webkit-calendar-picker-indicator:hover {
    opacity: 1;
}

.task-date-input:focus {
    outline: none;
    border-color: var(--color-primary);
    background: rgba(51, 65, 85, 0.7);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    color: var(--color-text-primary);
    background: rgba(51, 65, 85, 0.8);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
    background: rgba(71, 85, 105, 0.8);
}

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

.btn-danger:hover:not(:disabled) {
    background: #dc2626;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-icon {
    padding: var(--space-2);
    background: transparent;
    color: var(--color-text-tertiary);
}

.btn-icon:hover:not(:disabled) {
    color: var(--color-text-primary);
    background: rgba(51, 65, 85, 0.5);
}

/* 
   LISTA DE TAREAS
    */
.task-list-section {
    animation: fadeIn var(--transition-slow) ease-out 0.3s backwards;
    margin-bottom: var(--space-8);
}

.task-list-section:last-child {
    margin-bottom: 0;
}

.section-title {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-primary);
    margin-bottom: var(--space-4);
    padding-bottom: var(--space-3);
    border-bottom: 2px solid var(--color-border);
}

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

#completed-tasks-heading svg {
    color: var(--color-success);
}

.task-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
}

/* Estado Vacío */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-8) var(--space-4);
    text-align: center;
}

.empty-icon {
    color: var(--color-text-muted);
    opacity: 0.3;
    margin-bottom: var(--space-3);
}

.empty-message {
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-secondary);
    margin-bottom: var(--space-1);
}

.empty-hint {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* Elemento de Tarea */
.task-item {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    padding: var(--space-4);
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(12px);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
    animation: slideIn var(--transition-base) ease-out;
    cursor: grab;
}

.task-item:active {
    cursor: grabbing;
}

/* Drag and Drop States */
.task-item.dragging {
    opacity: 0.4;
    cursor: grabbing;
    transform: scale(0.95);
}

.task-list.drag-over {
    background: rgba(99, 102, 241, 0.05);
    border: 2px dashed var(--color-primary);
    border-radius: var(--radius-lg);
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.task-item:hover {
    border-color: var(--color-border-light);
    box-shadow: var(--shadow-md);
}

.task-item.completed {
    opacity: 0.7;
}

.task-item.completed .task-text {
    color: var(--color-text-tertiary);
}

/* Casilla de Verificación */
.task-checkbox {
    flex-shrink: 0;
    width: 24px;
    height: 24px;
    appearance: none;
    border: 2px solid var(--color-border-light);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-base);
    position: relative;
}

.task-checkbox:hover {
    border-color: var(--color-primary);
}

.task-checkbox:checked {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    border-color: var(--color-primary);
}

.task-checkbox:checked::after {
    content: '';
    position: absolute;
    top: 2px;
    left: 6px;
    width: 6px;
    height: 10px;
    border: solid white;
    border-width: 0 2px 2px 0;
    transform: rotate(45deg);
}

/* Contenido de Tarea */
.task-content {
    flex: 1;
    min-width: 0;
}

.task-text {
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-primary);
    word-wrap: break-word;
}

.task-description {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    margin-top: var(--space-2);
    padding: var(--space-2);
    line-height: 1.5;
    white-space: pre-wrap;
    word-wrap: break-word;
}

.task-date {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
    margin-top: var(--space-3);
    flex-wrap: wrap;
}

/* Badges de Fecha (Smart Status) */
.date-badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 2px 8px;
    border-radius: 12px;
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.02em;
}

/* Estado: Vencida */
.date-badge.overdue {
    background: rgba(220, 38, 38, 0.2);
    color: #f87171;
    border: 1px solid rgba(220, 38, 38, 0.3);
    animation: pulse-red 2s infinite;
}

/* Estado: Hoy */
.date-badge.today {
    background: rgba(234, 88, 12, 0.2);
    color: #fb923c;
    border: 1px solid rgba(234, 88, 12, 0.3);
}

/* Estado: Mañana */
.date-badge.tomorrow {
    background: rgba(202, 138, 4, 0.2);
    color: #facc15;
    border: 1px solid rgba(202, 138, 4, 0.3);
}

/* Estado: Futuro */
.date-badge.future {
    background: rgba(51, 65, 85, 0.5);
    color: #94a3b8;
    border: 1px solid var(--color-border);
}

@keyframes pulse-red {
    0% {
        box-shadow: 0 0 0 0 rgba(220, 38, 38, 0.4);
    }

    70% {
        box-shadow: 0 0 0 6px rgba(220, 38, 38, 0);
    }

    100% {
        box-shadow: 0 0 0 0 rgba(220, 38, 38, 0);
    }
}

/* Acciones de Tarea */
.task-actions {
    display: flex;
    gap: var(--space-2);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.task-item:hover .task-actions,
.task-item:focus-within .task-actions {
    opacity: 1;
}

/* 
   MODAL
    */
.modal {
    position: fixed;
    inset: 0;
    z-index: var(--z-modal);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-4);
}

.modal[hidden] {
    display: none;
}

.modal-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    animation: fadeIn var(--transition-base);
}

.modal-content {
    position: relative;
    width: 100%;
    max-width: 400px;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
    animation: scaleIn var(--transition-base) ease-out;
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-header {
    padding: var(--space-6);
    border-bottom: 1px solid var(--color-border);
}

.modal-title {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-primary);
}

.modal-body {
    padding: var(--space-6);
}

.modal-body p {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-4);
}

.modal-task-preview {
    padding: var(--space-3);
    background: rgba(51, 65, 85, 0.5);
    border-radius: var(--radius-md);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-primary);
}

.modal-footer {
    display: flex;
    gap: var(--space-3);
    padding: var(--space-6);
    border-top: 1px solid var(--color-border);
}

.modal-footer .btn {
    flex: 1;
}

/* 
   NOTIFICACIÓN TOAST
    */
.toast {
    position: fixed;
    bottom: var(--space-6);
    left: 50%;
    transform: translateX(-50%);
    z-index: var(--z-toast);
    padding: var(--space-4) var(--space-6);
    background: rgba(30, 41, 59, 0.95);
    backdrop-filter: blur(12px);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    color: var(--color-text-primary);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    animation: slideUp var(--transition-base) ease-out;
}

.toast[hidden] {
    display: none;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translate(-50%, 20px);
    }

    to {
        opacity: 1;
        transform: translate(-50%, 0);
    }
}

/* 
   DISEÑO RESPONSIVE
    */

/* Tablet y Desktop */
@media (min-width: 768px) {
    .app-container {
        display: grid;
        grid-template-columns: 420px 1fr;
        gap: var(--space-8);
        padding: var(--space-6);
        max-width: 1400px;
        margin: 0 auto;
    }

    .sidebar {
        position: sticky;
        top: var(--space-6);
        height: fit-content;
        max-height: calc(100vh - var(--space-12));
        overflow-y: auto;
    }

    .main-content {
        min-height: calc(100vh - var(--space-12));
    }

    .app-title {
        font-size: var(--font-size-2xl);
    }

    .task-form {
        padding: var(--space-6);
    }

    .header-content {
        padding: var(--space-6);
    }

    .filter-buttons {
        padding: var(--space-2);
    }
}

/* Desktop Grande */
@media (min-width: 1024px) {
    .app-container {
        grid-template-columns: 450px 1fr;
        gap: var(--space-10);
    }

    .app-title {
        font-size: var(--font-size-3xl);
    }
}

/* 
   ESTILOS DE IMPRESIÓN
    */
@media print {

    .task-form-section,
    .filter-section,
    .task-actions,
    .modal,
    .toast {
        display: none !important;
    }

    body {
        background: white;
        color: black;
    }

    .task-item {
        border: 1px solid #ccc;
        page-break-inside: avoid;
    }
}