Comment: The ball can move freely inside the box, and the black bricks can be controlled to move up and down, left and right through the direction key to collide with the ball. The specific implementation ideas and codes are as follows. Interested friends can refer to it. I hope it will be helpful for everyone to learn html5.
Demo address
Brief introduction
The ball can move freely inside the box
The black brick can be controlled to move up and down, left and right through the direction key to collide with the ball
Code implementation
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<!DOCTYPE html>
<html>
<head>
<title>Table tennis game</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;
}
//Crashed to the top
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;
}
//Crash to the left
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;
}
//Crash to the right
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;
}
//Crash down
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.fillStyle="rgb(255,0,0)";
//ctx.lineWidth=ball_radius;
ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true);
ctx.fill();//note
ctx.fillStyle="rgb(0,0,0)";
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>
<canvas></canvas>
</body>
</html>
difficulty
Collision detection and collision treatment of small balls and bricks
Decompose the brick into 4 line segments
Collision detection is performed on the ball and each line segment respectively.
Collision detection of balls and line segments is introduced in another article.