:root {
    --color-primario: #3483fa;
    --color-primario-oscuro: #2968c8;

    --color-fondo: #f5f5f5;
    --color-superficie: #ffffff;

    --color-texto: #333;
    --color-texto-secundario: #666;

    --color-borde: #e0e0e0;

    --color-error-bg: #ffe5e5;
    --color-error: #d32f2f;

    --color-vacio: #999;

    --border-radius: 8px;
    --sombra: 0 2px 6px rgba(0,0,0,0.1);
    --transicion: all 0.2s ease;
}


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

body {
    font-family: Arial, sans-serif;
    background-color: var(--color-fondo);
    color: var(--color-texto);
}


nav {
    background-color: var(--color-primario);
    padding: 15px;
}

nav a {
    color: white;
    text-decoration: none;
    margin-right: 10px;
    padding: 6px 10px;
    border-radius: 4px;
    transition: var(--transicion);
}

nav a:hover {
    background-color: var(--color-primario-oscuro);
}


.container {
    max-width: 1100px;
    margin: 30px auto;
    padding: 20px;
}


input[type="text"],
input[type="search"],
select {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--color-borde);
    border-radius: var(--border-radius);
    transition: var(--transicion);
}

input:focus,
select:focus {
    outline: none;
    border-color: var(--color-primario);
    box-shadow: 0 0 0 2px rgba(52,131,250,0.2);
}


button {
    background-color: var(--color-primario);
    color: white;
    border: none;
    padding: 10px 15px;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transicion);
}

button:hover {
    background-color: var(--color-primario-oscuro);
}


.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
}


.card {
    background: var(--color-superficie);
    border: 1px solid var(--color-borde);
    border-radius: var(--border-radius);
    padding: 15px;
    box-shadow: var(--sombra);
    transition: var(--transicion);
    text-align: center;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.15);
}

.card img {
    width: 100px;
    height: 100px;
}

.card h3 {
    margin-top: 10px;
    text-transform: capitalize;
}

.card span {
    color: var(--color-texto-secundario);
    font-size: 14px;
}


.header-index {
    background: var(--color-primario);
    color: white;
    text-align: center;
    padding: 40px 20px;
}

.subtitulo {
    margin-top: 10px;
    opacity: 0.9;
}

.seccion-titulo {
    margin-bottom: 20px;
    text-align: center;
}

#menu a {
    text-decoration: none;
    color: inherit;
}


.layout {
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 20px;
    max-width: 1200px;
    margin: 20px auto;
    padding: 0 20px;
}

.sidebar {
    background: var(--color-superficie);
    padding: 15px;
    border-radius: var(--border-radius);
    box-shadow: var(--sombra);
    height: fit-content;
}

.filtro-grupo {
    margin-top: 15px;
}

.btn-reset {
    margin-top: 20px;
    width: 100%;
}

#contenedor {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 20px;
}

#form-tareas {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
}

#inputTarea {
    flex: 1;
}

#lista-tareas li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--color-superficie);
    border: 1px solid var(--color-borde);
    padding: 10px;
    border-radius: var(--border-radius);
    margin-top: 10px;
    box-shadow: var(--sombra);
}

#lista-tareas li div {
    display: flex;
    align-items: center;
    gap: 10px;
}

#lista-tareas input[type="checkbox"] {
    width: 16px;
    height: 16px;
}

#lista-tareas span {
    font-size: 14px;
}

.completada span {
    text-decoration: line-through;
    opacity: 0.6;
}

#lista-tareas button {
    background-color: crimson;
    padding: 6px 10px;
    font-size: 12px;
}


.loading {
    text-align: center;
    animation: parpadeo 1s infinite alternate;
}

@keyframes parpadeo {
    from { opacity: 0.4; }
    to { opacity: 1; }
}

.error {
    background-color: var(--color-error-bg);
    color: var(--color-error);
    border: 1px solid var(--color-error);
    padding: 10px;
    border-radius: var(--border-radius);
    text-align: center;
}

.vacio {
    text-align: center;
    color: var(--color-vacio);
    padding: 20px;
}


@media (max-width: 768px) {
    .layout {
        grid-template-columns: 1fr;
    }

    .container {
        padding: 10px;
    }
}