Javascript:射击小游戏

Javascript:射击小游戏

脚本说明:
第一步:把如下代码加入<body>区域中
<SCRIPT LANGUAGE="JavaScript">

// ---- Make array
function MakeArray( n){
   this.length = n;
   for (var i = 1; i <= n; i++) {
     this[i] = 0
   }
   return this
}

// ----- poor man's random number
var d0 = new Date();
var r0 = d0.getSeconds();
function poor_rand(){
   d1 = new Date();
   r0 = (r0 * r0 + r0 + d1.getSeconds()) % 3721 ;
   return r0 % width_n;
}

// ---- Parameters of game
var height_n = 8;
var width_n =5;

// ---- state of game
var enemy = new MakeArray( width_n); // enemy positions
var wtime; // wait time
var score; // points
var gameover; // in case of gameover set to true

// ----- Make the battlefield.
document.write( "<FORM NAME='fm1'>");
document.write( "<INPUT TYPE='text' NAME='message' SIZE=20>");
document.write( "</FORM>");
document.write( "<FORM NAME='fm2'><TABLE>");
for( var i=0; i<height_n; i++){
   document.write( "<TR>");
   for( var j=0;j<width_n; j++){
     document.write( "<TD><CENTER><INPUT TYPE='radio'></CENTER></TD>");
   }
   document.write( "</TR>");
}
document.write( "<TR>");
for( var j=0;j<width_n; j++){
   document.write( "<TD><INPUT TYPE='button' VALUE='A' onClick='fire("
     + j + ")'></TD>");
}
document.write( "</TR>");
document.write( "</TABLE>");
document.write( "<INPUT TYPE='button' VALUE='START' onClick='game_start()'>");
document.write( "</FORM>");

// ----- game main timer event
// -----   enemy come one step
function come(){
   var n = poor_rand();
   document.fm2.elements[ width_n * enemy[n+1] + n].checked = true;
   enemy[n+1]++;
   if( enemy[n+1] < height_n){
     setTimeout("come()", wtime);
   }else{
    gameover = true;
    document.fm1.message.value = "GAME OVER:" + score ;
   }
}

// ----- Fire the n th beam
function fire( n){
   if( gameover ) return;
   for( var i=0; i<enemy[n+1]; i++){ // clear enemy
     document.fm2.elements[ width_n * i + n].checked = false;
   }
   score += enemy[ n+1];
   document.fm1.message.value = "Points:" + score;
   enemy[ n+1] = 0;
   if( wtime > 50){ wtime -= 10};
}

// ---- initialize & start game
function game_start(){
  for( var n=0; n<width_n; n++){
     for( var i=0; i<enemy[n+1]; i++){
       document.fm2.elements[ width_n * i + n].checked = false;
     }
     enemy[n+1] = 0;
   }
   wtime = 150;
   score = 0;
   gameover = false;
   document.fm1.message.value = "Points:" + score;
   setTimeout("come()", wtime);
}

// -->

</SCRIPT>

第二步:把<body>区域中的内容改为:
<BODY bgcolor="#fef4d9" onLoad="document.forms[0].guess.focus(); document.forms[0].guess.select()">