:root{
    --bg-color: #f4f7f6;
    --text-color: #2d3436;
    --white: #ffffff;
    --sombra: 0 4px 6px rgba(0,0,0,0.1);
    --sombra-oscura: 0 4px 6px rgba(0,0,0,0.4);
    --transition: all 0.1s;
    --color-excel: #217356;
    --cabecera: #0d2236;
}

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

body{
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
    display: flex;
    flex-direction: column;
    min-height: 100dvh;
}

header{
    background-color: var(--cabecera);
    color: var(--white);
    text-align: center;
    padding: .5rem 1rem;
    box-shadow: var(--sombra);
    font-size: .9rem;
    width: 100%;
}
main{
    margin: 1rem auto;
    padding:3rem;
    flex: 1;
    width: 100%;
}
footer{
    background-color: var(--cabecera);
    color: var(--white);
    text-align: center;
    padding: .5rem 1rem;
    margin-top: 10px;
    box-shadow: var(--sombra);
    font-size: .8rem;
    width: 100%;
}

.grid-principal{
    display: grid;
    grid-template-columns: repeat(auto-fit,minmax(300px,1fr));
    gap: 1.5rem;
}

.tarjeta{
    background-color: var(--white);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--sombra);
    border-top: 5px solid var(--color-excel);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}
.tarjeta:hover{
    box-shadow: var(--sombra-oscura);
}