1 - An angle in pureCSS
div {
--angle: 150deg; /* CHANGE THIS VALUE TO THE ANGLE YOU WANT */
}
div {
height: 300px;
width: 600px;
overflow: hidden;
position: relative;
background: crimson;
border-radius: 300px 300px 0 0;
border: 1px solid crimson;
}
div::before {
height: inherit;
width: inherit;
position: absolute;
content: "";
background-color: white;
transform-origin: 50% 100%;
transform: rotate(var(--angle));
}