復制代碼代碼如下: !-- To change this template, choose Tools | Templates and open the template in the editor. -- !DOCTYPE html html head title 乒乓球游戲 /title meta http-equiv="Content-Type" content="text/html; charset=utf-8" script var ctx; var canvas; var ball_x=10; var ball_y=10; var ball_radius=10; var ball_vx=10; var ball_vy=8; var wall_x=30; var wall_y=40; var wall_width=30; var wall_height=60; var box_x=0; var box_y=0; var box_width=300; var box_height=300; var bound_left=box_x+ball_radius; var bound_right=box_x+box_width-ball_radius; var bound_top=box_y+ball_radius; var bound_bottom=box_y+box_height-ball_radius; var unit=10; function intersect(sx, sy, fx, fy, cx, cy, rad) { var dx; var dy; var t; var rt; dx = fx - sx; dy = fy - sy; t = 0.0 - (((sx - cx) * dx + (sy - cy) * dy) / (dx * dx + dy * dy)); if (t 0.0) { t = 0.0; } else if (t 1.0) t = 1.0; var dx1 = (sx + t * dx) - cx; var dy1 = (sy + t * dy) - cy; var rt = dx1 * dx1 + dy1 * dy1; if (rt rad * rad) return true; else return false; } function move_ball() { ball_x=ball_x+ball_vx; ball_y=ball_y+ball_vy; if(ball_x bound_left) { ball_x=bound_left; ball_vx=-ball_vx; } if(ball_x bound_right) { ball_x=bound_right; ball_vx=-ball_vx; } if(ball_y bound_top) { ball_y=bound_top; ball_vy=-ball_vy; } if(ball_y bound_bottom) { ball_y=bound_bottom; ball_vy=-ball_vy; } //撞到上邊 if(intersect(wall_x,wall_y,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius)) { ball_y=wall_y-ball_radius; ball_vy=-ball_vy; } //撞到左邊 if(intersect(wall_x,wall_y,wall_x,wall_y+wall_height,ball_x,ball_y,ball_radius)) { ball_x=wall_x-ball_radius; ball_vx=-ball_vx; } //撞到右邊 if(intersect(wall_x+wall_width,wall_y,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius)) { ball_x=wall_x+wall_width+ball_radius; ball_vx=-ball_vx; } //撞到下邊 if(intersect(wall_x,wall_y+wall_height,wall_x+wall_width,wall_y+wall_height,ball_x,ball_y,ball_radius)) { ball_y=wall_y+wall_height+ball_radius; ball_vy=-ball_vy; } } function move_wall(ev) { var keyCode; if(event==null) { keyCode=window.event.keyCode; window.event.preventDefault(); } else { keyCode=event.keyCode; event.preventDefault(); } switch(keyCode) { case 37://left; wall_x-=unit; if(wall_x bound_left) wall_x=bound_left; break; case 38://up wall_y-=unit; if(wall_y bound_top) wall_y=bound_top; break; case 39://right wall_x+=unit; if(wall_x+wall_width bound_right) wall_x=bound_right-wall_width; break; case 40://down wall_y+=unit; if(wall_y+wall_height bound_bottom) wall_y=bound_bottom-wall_height; break; default: break; } } function draw_all() { ctx.beginPath(); ctx.clearRect(box_x,box_y,box_width,box_height); ctx.fill ; //ctx.lineWidth=ball_radius; ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true); ctx.fill();//note ctx.fill ; ctx.fillRect(wall_x,wall_y,wall_width,wall_height); ctx.strokeRect(box_x,box_y,box_width,box_height); } function init() { canvas=document.getElementById('canvas'); ctx=canvas.getContext('2d'); draw_all(); setInterval(draw_all,100); setInterval(move_ball,50); window.addEventListener('keydown',move_wall,false);//note } /script /head body onLoad="init();" canvas id="canvas" width="300" height="300" /canvas /body /html
