width: 500px;
height: 500px;
background:
radial-gradient(circle at 100% 50%, rgb(69 255 144 / 0) 20%, rgb(69 168 255 / 1) 21%, rgb(69 168 255 / 1) 34%, rgb(255 255 255 / 0) 35%) 0px 0px / 75px 100px repeat repeat, /* Left Wave */
radial-gradient(circle at 0% 50%, rgb(69 255 144 / 0) 20%, rgb(69 168 255 / 1) 21%, rgb(69 168 255 / 1) 34%, rgb(255 255 255 / 0) 35%) 0px 50px / 75px 100px repeat repeat; /* Right Wave */