:root {
    --sep-height: 55px;
    --color-white: #fff;
    --color-gray:  #f7f8fc;
}

/* Fond blanc qui descend en diagonale vers le gris */
.sec-white {
    position: relative;
    background: var(--color-white);
}
.sec-white.sec-to-gray::after {
    content: '';
    position: absolute;
    bottom: 0; left: 0;
    width: 100%;
    height: var(--sep-height);
    background: var(--color-gray);
    clip-path: polygon(0 100%, 100% 0, 100% 100%);
    pointer-events: none;
    z-index: 2;
}

/* Fond gris qui descend en diagonale vers le blanc */
.sec-gray {
    position: relative;
    background: var(--color-gray);
}
.sec-gray.sec-to-white::after {
    content: '';
    position: absolute;
    bottom: 0; left: 0;
    width: 100%;
    height: var(--sep-height);
    background: var(--color-white);
    clip-path: polygon(0 0, 100% 100%, 0 100%);
    pointer-events: none;
    z-index: 2;
}

@media (max-width: 768px) {
    :root { --sep-height: 35px; }
}