/* =========================
   RESET
========================= */
*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', sans-serif;
}

/* =========================
   BODY
========================= */
body{

    background: linear-gradient(-45deg,
    #667eea,
    #764ba2,
    #6a11cb,
    #2575fc);

    background-size: 400% 400%;

    animation: fondoAnimado 12s ease infinite;

    color: white;

    min-height: 100vh;
}

/* FONDO ANIMADO */
@keyframes fondoAnimado{

    0%{
        background-position: 0% 50%;
    }

    50%{
        background-position: 100% 50%;
    }

    100%{
        background-position: 0% 50%;
    }
}

/* =========================
   CABECERA
========================= */
.cabecera{

    text-align: center;

    padding: 35px;

    background: rgba(0,0,0,0.25);

    backdrop-filter: blur(8px);

    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

.cabecera h1{

    font-size: 50px;

    animation: brillo 2s infinite alternate;
}

/* EFECTO BRILLO */
@keyframes brillo{

    from{
        text-shadow: 0 0 10px white;
    }

    to{
        text-shadow: 0 0 25px yellow;
    }
}

/* =========================
   MENU
========================= */
.menu{

    display: flex;

    justify-content: center;

    gap: 20px;

    padding: 18px;

    background: rgba(0,0,0,0.25);

    backdrop-filter: blur(8px);

    position: sticky;

    top: 0;

    z-index: 1000;
}

/* LINKS */
.menu a{

    color: white;

    text-decoration: none;

    padding: 10px 18px;

    border-radius: 12px;

    transition: 0.4s;
}

/* HOVER MENU */
.menu a:hover{

    background: rgba(255,255,255,0.2);

    color: yellow;

    transform: translateY(-3px);

    box-shadow: 0 0 12px rgba(255,255,255,0.5);
}

/* =========================
   CONTENEDOR PRINCIPAL
========================= */
.contenedor-principal{

    width: 95%;

    margin: 40px auto;

    display: flex;

    gap: 30px;

    align-items: flex-start;
}

/* =========================
   CONTENIDO
========================= */
.contenido{

    flex: 3;
}

/* TITULO */
.titulo{

    text-align: center;

    margin-bottom: 35px;

    font-size: 40px;

    animation: brillo 2s infinite alternate;
}

/* =========================
   LECCIONES
========================= */
.contenedor-lecciones{

    display: grid;

    grid-template-columns: repeat(auto-fit,minmax(300px,1fr));

    gap: 25px;
}

/* TARJETAS */
.leccion{

    background: rgba(255,255,255,0.15);

    backdrop-filter: blur(10px);

    border-radius: 20px;

    padding: 25px;

    box-shadow: 0 10px 25px rgba(0,0,0,0.3);

    transition: 0.5s;

    animation: flotar 4s ease-in-out infinite;
}

/* EFECTO HOVER */
.leccion:hover{

    transform: translateY(-10px) scale(1.03);

    box-shadow: 0 15px 35px rgba(0,0,0,0.5);
}

/* ANIMACION */
@keyframes flotar{

    0%{
        transform: translateY(0px);
    }

    50%{
        transform: translateY(-8px);
    }

    100%{
        transform: translateY(0px);
    }
}

/* TITULOS */
.leccion h4{

    font-size: 28px;

    margin-bottom: 15px;

    color: #ffe600;
}

/* TEXTO */
.leccion p{

    line-height: 1.7;

    margin-bottom: 15px;

    color: #f1f1f1;
}

/* BOTON */
.leccion a{

    display: inline-block;

    padding: 12px 20px;

    background: linear-gradient(45deg,#ff6b6b,#ffb347);

    color: white;

    text-decoration: none;

    border-radius: 12px;

    transition: 0.4s;
}

/* HOVER BOTON */
.leccion a:hover{

    transform: scale(1.08);

    box-shadow: 0 0 15px rgba(255,255,255,0.6);
}

/* =========================
   BARRA LATERAL
========================= */
.barra-lateral{

    flex: 1;

    background: rgba(255,255,255,0.15);

    backdrop-filter: blur(10px);

    padding: 25px;

    border-radius: 20px;

    box-shadow: 0 10px 25px rgba(0,0,0,0.3);

    animation: flotar 5s ease-in-out infinite;
}

/* TITULO */
.barra-lateral h3{

    margin-bottom: 20px;

    font-size: 28px;

    color: #ffe600;
}

/* LISTA */
.barra-lateral ul{

    list-style: none;
}

/* ITEMS */
.barra-lateral li{

    margin-bottom: 15px;
}

/* LINKS */
.barra-lateral a{

    color: white;

    text-decoration: none;

    transition: 0.3s;
}

/* HOVER */
.barra-lateral a:hover{

    color: yellow;

    padding-left: 8px;
}

/* =========================
   PIE DE PAGINA
========================= */
.pie-pagina{

    text-align: center;

    padding: 20px;

    margin-top: 40px;

    background: rgba(0,0,0,0.3);

    backdrop-filter: blur(8px);
}

/* =========================
   RESPONSIVE
========================= */
@media(max-width:900px){

    .contenedor-principal{

        flex-direction: column;
    }

    .menu{

        flex-wrap: wrap;
    }

    .cabecera h1{

        font-size: 35px;
    }

    .titulo{

        font-size: 32px;
    }
}