*{
    margin:0;
    padding:0;
    box-sizing:border-box;
    font-family:Arial, Helvetica, sans-serif;
}

body{
    background:#f4f6f9;
}

/* CONTENEDOR GENERAL */
.contenedor-principal{
    display:flex;
    min-height:100vh;
}

/* SIDEBAR */
.sidebar{
    width:260px;
    background:linear-gradient(180deg,#0d1b2a,#1b263b);
    color:white;
    padding:30px 20px;
    box-shadow:4px 0 10px rgba(0,0,0,0.2);
}

.logo{
    font-size:28px;
    font-weight:bold;
    text-align:center;
    margin-bottom:40px;
    letter-spacing:2px;
}

.menu{
    list-style:none;
}

.menu li{
    margin-bottom:18px;
}

.menu li a{
    display:block;
    padding:14px;
    text-decoration:none;
    color:white;
    background:rgba(255,255,255,0.08);
    border-radius:10px;
    transition:0.3s;
    font-size:16px;
}

.menu li a:hover{
    background:#00b4d8;
    transform:translateX(5px);
}

/* CONTENIDO */
.contenido{
    flex:1;
    padding:35px;
}

/* BIENVENIDA */
.bienvenida{
    background:linear-gradient(135deg,#0077b6,#00b4d8);
    color:white;
    padding:35px;
    border-radius:15px;
    box-shadow:0 8px 20px rgba(0,0,0,0.15);
    margin-bottom:30px;
}

.bienvenida h1{
    font-size:36px;
    margin-bottom:10px;
}

.bienvenida p{
    font-size:18px;
}

/* TARJETAS */
.cards{
    display:grid;
    grid-template-columns:repeat(auto-fit,minmax(280px,1fr));
    gap:25px;
}

.card{
    background:white;
    padding:25px;
    border-radius:15px;
    box-shadow:0 5px 15px rgba(0,0,0,0.08);
    transition:0.3s;
}

.card:hover{
    transform:translateY(-5px);
}

.card h2{
    color:#0077b6;
    margin-bottom:15px;
}

.card p{
    color:#444;
    line-height:1.7;
    font-size:15px;
}

/* FOOTER */
.footer{
    margin-top:40px;
    text-align:center;
    color:#666;
    font-size:14px;
    padding:15px;
}

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

    .contenedor-principal{
        flex-direction:column;
    }

    .sidebar{
        width:100%;
    }

    .contenido{
        padding:20px;
    }

    .bienvenida h1{
        font-size:28px;
    }
}