当您按下键盘上的向下箭头按钮时，nav-down属性用于向下移动。您可以尝试运行以下代码来实现CSS nav-down属性
<!DOCTYPE html>
<html>
<head>
<style>
button {
position: absolute;
}
button#btn1 {
top: 10%;
left: 15%;
nav-index: 1;
nav-right: #btn2;
nav-left: #btn4;
nav-down: #btn2;
nav-up: #btn4;
}
button#btn2 {
top: 30%;
left: 30%;
nav-index: 2;
nav-right: #btn3;
nav-left: #btn1;
nav-down: #btn3;
nav-up: #btn1;
}
button#btn3 {
top: 50%;
left: 15%;
nav-index: 3;
nav-right: #btn4;
nav-left: #btn2;
nav-down: #btn4;
nav-up: #btn2;
}
button#btn4 {
top: 30%;
left: 0%;
nav-index: 4;
nav-right: #btn1;
nav-left: #btn3;
nav-down: #btn1;
nav-up: #btn3;
}
</style>
</head>
<body>
<button id = "btn1">Result1</button>
<button id = "btn2">Result2</button>
<button id = "btn3">Result3</button>
<button id = "btn4">Result4</button>
</body>
</html>