Simply use the keyboard to control the movement of blocks

<span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">html </span><span style="color: #ff0000;">lang</span><span style="color: #0000ff;">="en"</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="UTF-8"</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>键盘控制方块移动<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
    #box</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
        width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
        height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
        background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> green</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
        position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> relative</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
        left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #ff0000;">
        top</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
    <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">id</span><span style="color: #0000ff;">="box"</span><span style="color: #0000ff;">></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">script</span><span style="color: #0000ff;">></span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;"> var box=document.getElementById('box');//此部分代码的效果会用小小的停顿，下面的为改进代码</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;"> var l=0;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;"> var t=0;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;"> document.onkeydown=function(){</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     var e=window.event||ev;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     // console.log(e.keyCode);</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     if (e.keyCode==37) {</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         l-=10;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         box.style.                               </span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         left=l+'px';</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     }</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     if (e.keyCode==38) {</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         t-=10;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         box.style.top=t+'px';</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     }</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     if (e.keyCode==39) {</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         l+=10;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         box.style.left=l+'px';</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     }</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     if (e.keyCode==40) {</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         t+=10;</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">         box.style.top=t+'px';</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">     }</span>
        <span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;"> }</span>
        <span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> div</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">document.getElementById(</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">box</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">);
        </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> s</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">,left</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">,right</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">,bottom</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;</span><span style="background-color: #f5f5f5; color: #008000;">//</span><span style="background-color: #f5f5f5; color: #008000;">用top不可以，为保留字；</span>
        <span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> timer</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #0000ff;">null</span><span style="background-color: #f5f5f5; color: #000000;">,x</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">50</span><span style="background-color: #f5f5f5; color: #000000;">,y</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">50</span><span style="background-color: #f5f5f5; color: #000000;">;
        timer</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">setInterval(</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(){
            </span><span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;"> (left</span><span style="background-color: #f5f5f5; color: #000000;">==</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">) {
                x</span><span style="background-color: #f5f5f5; color: #000000;">-=</span><span style="background-color: #f5f5f5; color: #000000;">5</span><span style="background-color: #f5f5f5; color: #000000;">;
                div.style.left</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">x</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">px</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">;
            }
            </span><span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;"> (right</span><span style="background-color: #f5f5f5; color: #000000;">==</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">) {
                x</span><span style="background-color: #f5f5f5; color: #000000;">+=</span><span style="background-color: #f5f5f5; color: #000000;">5</span><span style="background-color: #f5f5f5; color: #000000;">;
                div.style.left</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">x</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">px</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">;
            }
            </span><span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;"> (s</span><span style="background-color: #f5f5f5; color: #000000;">==</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">) {
                y</span><span style="background-color: #f5f5f5; color: #000000;">-=</span><span style="background-color: #f5f5f5; color: #000000;">5</span><span style="background-color: #f5f5f5; color: #000000;">;
                div.style.top</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">y</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">px</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">;
            }
            </span><span style="background-color: #f5f5f5; color: #0000ff;">if</span><span style="background-color: #f5f5f5; color: #000000;"> (bottom</span><span style="background-color: #f5f5f5; color: #000000;">==</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">) {
                y</span><span style="background-color: #f5f5f5; color: #000000;">+=</span><span style="background-color: #f5f5f5; color: #000000;">5</span><span style="background-color: #f5f5f5; color: #000000;">;
                div.style.top</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">y</span><span style="background-color: #f5f5f5; color: #000000;">+</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">px</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">;
            }
        },</span><span style="background-color: #f5f5f5; color: #000000;">20</span><span style="background-color: #f5f5f5; color: #000000;">)
        document.onkeydown</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(ev){
            </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> e</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">ev</span><span style="background-color: #f5f5f5; color: #000000;">||</span><span style="background-color: #f5f5f5; color: #000000;">window.event;
            </span><span style="background-color: #f5f5f5; color: #0000ff;">switch</span><span style="background-color: #f5f5f5; color: #000000;">(e.keyCode){
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">37</span><span style="background-color: #f5f5f5; color: #000000;">:
                    left</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">38</span><span style="background-color: #f5f5f5; color: #000000;">:
                    s</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">39</span><span style="background-color: #f5f5f5; color: #000000;">:
                    right</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">40</span><span style="background-color: #f5f5f5; color: #000000;">:
                    bottom</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">1</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">default</span><span style="background-color: #f5f5f5; color: #000000;">:
                    alert(</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">请按方向键</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">);
            }
        }
        document.onkeyup</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #0000ff;">function</span><span style="background-color: #f5f5f5; color: #000000;">(ev){
            </span><span style="background-color: #f5f5f5; color: #0000ff;">var</span><span style="background-color: #f5f5f5; color: #000000;"> e</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">ev</span><span style="background-color: #f5f5f5; color: #000000;">||</span><span style="background-color: #f5f5f5; color: #000000;">window.event;
            </span><span style="background-color: #f5f5f5; color: #0000ff;">switch</span><span style="background-color: #f5f5f5; color: #000000;">(e.keyCode){
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">37</span><span style="background-color: #f5f5f5; color: #000000;">:
                    left</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">38</span><span style="background-color: #f5f5f5; color: #000000;">:
                    s</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">39</span><span style="background-color: #f5f5f5; color: #000000;">:
                    right</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">case</span> <span style="background-color: #f5f5f5; color: #000000;">40</span><span style="background-color: #f5f5f5; color: #000000;">:
                    bottom</span><span style="background-color: #f5f5f5; color: #000000;">=</span><span style="background-color: #f5f5f5; color: #000000;">0</span><span style="background-color: #f5f5f5; color: #000000;">;
                    </span><span style="background-color: #f5f5f5; color: #0000ff;">break</span><span style="background-color: #f5f5f5; color: #000000;">;
                </span><span style="background-color: #f5f5f5; color: #0000ff;">default</span><span style="background-color: #f5f5f5; color: #000000;">:
                    alert(</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">请按方向键</span><span style="background-color: #f5f5f5; color: #000000;">'</span><span style="background-color: #f5f5f5; color: #000000;">);
            }
        }
    </span><span style="color: #0000ff;"></</span><span style="color: #800000;">script</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>

<span style="color: #0000ff;"></</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>