闪屏还可以这样玩

Aim.prototype = {
......
        // 获取准心的位置，以及获胜的概率
        getInfo: function() {
            return {
                x: this.drawX + this.moveX + this.width / 2,
                y: this.drawY + this.height / 2
            }
        },
......
}

//发射了，并还在运动时间内
if (this.isFired && this.t < this.duration) {
    //移动的时候根据时间缩小宽高
    this.width -= this.t * 15;
    this.height -= this.t * 15;
    //最终位置
    this.endpos[0] = this.finalpos[0] - this.width / 2;
    this.endpos[1] = this.finalpos[1] - this.height / 2;
    //发射位置
    this.startpos = [this.drawX, this.drawY];
    //计算控制点位置
    this.cp = [
        (this.startpos[0] + this.endpos[0]) / 2 - (this.startpos[1] - this.endpos[1]) * this.curveness,
        (this.startpos[1] + this.endpos[1]) / 2 - (this.endpos[0] - this.startpos[0]) * this.curveness
    ];
    //通过贝塞尔公式获得每个时间t的位置
    var x = quadraticBezier(this.startpos[0], this.cp[0], this.endpos[0], this.t);
    var y = quadraticBezier(this.startpos[1], this.cp[1], this.endpos[1], this.t);
    //时间t
    this.t += 0.2;
 
    this.drawX = Math.floor(x);
    this.drawY = Math.floor(y);
}

Goalkeeper.prototype = {
    update: function() {
        // 预备阶段
        if (this.isReady) {
            this.srcY = this.height * this.curFrame;
            //控制准备状态的帧数
            if (this.curFrame < this.frameNum - 1) {
                this.curFrame++;
            } else {
                this.curFrame = 0;
            }
        } else {
            // 准备扑球，可进球可不进
            if (this.isKeepBall) {
                this.curFrame = 12
            } else {
                this.curFrame = 13
            }
            this.srcY = this.height * this.curFrame;
        }
    },
    draw: function(gamectx) {
        if (this.visible) {
            //绘制守门员
            gamectx.drawImage(SpriteTool.goalkeeperSprite, this.srcX, this.srcY, this.width, this.height, this.drawX, this.drawY, this.width, this.height);
        }
    },
}

var getRandomPercent = function(probability) {
    var probability = probability * 100 || 1;
    var odds = Math.floor(Math.random() * 100);
    if (probability === 1) { return true };
    if (odds < probability) {
        return true;
    } else {
        return false;
    }
}

//判断是否进球
var info = this.aim.getInfo();
// 球停止了，且被扑中了
if (this.ball.isStop && info.result == false) {

    this.keeper.catchball();
    this.keeper.keepBall(info.x);
    this.ball.hide();
    //球停止了，且进球了
} else if (this.ball.isStop && info.result) {
    this.keeper.catchball();
    this.ball.hide();
    // 进球的时候，球在门框的位置
    if (this.aim.moveX > 0) {
        this.ballstage.drawBallInRight();
    } else {
        this.ballstage.drawBallInLeft();
    }
}

//控制变量
uniform float radius; //螺旋半径
uniform float angle;  //螺旋角度
uniform vec2 center;  //螺旋中心点
uniform vec2 texSize; //螺旋画布大小
uniform sampler2D texture; //纹理素材
varying vec2 texCoord; //坐标轴

void main() {
   //更新坐标轴xy
    vec2 coord = texCoord * texSize;
    coord -= center;
    float distance = length(coord);
    if (distance < radius) {
        float percent = (radius - distance) / radius;
        float theta = percent * percent * angle;
        float s = sin(theta);
        float c = cos(theta);
        
        coord = vec2(
            coord.x * c - coord.y * s,
            coord.x * s + coord.y * c
        );
    }
    coord += center;
    //改变顶点
    gl_FragColor = texture2D(texture, coord / texSize);
    vec2 clampedCoord = clamp(coord, vec2(0.0), texSize);
    if (coord != clampedCoord) {
        /* fade to transparent if we are outside the image */
        gl_FragColor.a *= max(0.0, 1.0 - length(coord - clampedCoord));
    }
}