//设置按键事件映射，这样按下键的时候就会触发对应的事件，具体来说就是触发对应的move，只有2和0.5
document.onkeydown = function(e) {
//eval生成的JavaScript代码，在这里就被执行了
eval(keycom[(e ? e : event).keyCode]);
};
//这样看来的话，这几乎是一个递归。。。
start();
//设置俄罗斯方块下落定时器，500毫秒触发一次，调节这里的数字可以调整游戏之中俄罗斯方块下落的快慢
run = setInterval("down()", 500);
</script>
</body>
</html>
下面给出原作者代码，60行
<!doctype html><html><head></head><body>
<div></div>
<script>
var map=eval("["+Array(23).join("0x801,")+"0xfff]");
var tatris=[[0x6600],[0x2222,0xf00],[0xc600,0x2640],[0x6c00,0x4620],[0x4460,0x2e0,0x6220,0x740],[0x2260,0xe20,0x6440,0x4700],[0x2620,0x720,0x2320,0x2700]];
var keycom={"38":"rotate(1)","40":"down()","37":"move(2,1)","39":"move(0.5,-1)"};
var dia, pos, bak, run;
function start(){
dia=tatris[~~(Math.random()*7)];
bak=pos={fk:[],y:0,x:4,s:~~(Math.random()*4)};
rotate(0);
}
function over(){
document.onkeydown=null;
clearInterval(run);
alert("GAME OVER");
}
function update(t){
bak={fk:pos.fk.slice(0),y:pos.y,x:pos.x,s:pos.s};
if(t) return;
for(var i=0,a2=""; i<22; i++)
a2+=map[i].toString(2).slice(1,-1)+"<br/>";
for(var i=0,n; i<4; i++)
if(/([^0]+)/.test(bak.fk[i].toString(2).replace(/1/g,"\u25a1")))
a2=a2.substr(0,n=(bak.y+i+1)*15-RegExp.$_.length-4)+RegExp.$1+a2.slice(n+RegExp.$1.length);
document.getElementById("box").innerHTML=a2.replace(/1/g,"\u25a0").replace(/0/g,"\u3000");
}
function is(){
for(var i=0; i<4; i++)
if((pos.fk[i]&map[pos.y+i])!=0) return pos=bak;
}
function rotate(r){
var f=dia[pos.s=(pos.s+r)%dia.length];
for(var i=0; i<4; i++)
pos.fk[i]=(f>>(12-i*4)&15)<<pos.x;
update(is());
}
function down(){
++pos.y;
if(is()){
for(var i=0; i<4 && pos.y+i<22; i++)
if((map[pos.y+i]|=pos.fk[i])==0xfff)
map.splice(pos.y+i,1), map.unshift(0x801);
if(map[1]!=0x801) return over();
start();
}
update();
}
function move(t,k){
pos.x+=k;
for(var i=0; i<4; i++)
pos.fk[i]*=t;
update(is());
}
document.onkeydown=function(e){
eval(keycom[(e?e:event).keyCode]);
};
start();
run=setInterval("down()",400);
</script></body></html>