上篇讲到了，可以设置一定角度发炮弹了！这时接着做，首先我们把炮弹去掉，只要炮弹出来舞台左、右和下我们就将该MC去掉。

代码：

Mouse.hide();
gravity = 2;
attachMovie("crosshair", "crosshair", 1);
attachMovie("tank", "tank", 2, {_x:230, _y:350});
crosshair.onEnterFrame = function() {
    this._x = _xmouse;
    this._y = _ymouse;
};
tank.onEnterFrame = function() {
    mousex = _xmouse-this._x;
    mousey = (_ymouse-this._y)*-1;
    angle = Math.atan(mousey/mousex)/(Math.PI/180);
    if (mousex<0) {
        angle += 180;
    }
    if (mousex>=0 && mousey<0) {
        angle += 360;
    }
    if (angle>160) {
        angle = 160;
    }
    if (angle<20) {
        angle = 20;
    }
    firepower = Math.sqrt(mousex*mousex+mousey*mousey);
    if (firepower>200) {
        firepower = 200;
    }
    this.cannon._rotation = angle*-1;
};
function onMouseDown() {
    angle = tank.cannon._rotation-1;
    start_ball_x = tank._x+48*Math.cos(angle*Math.PI/180);
    start_ball_y = tank._y+48*Math.sin(angle*Math.PI/180);
    cannonball_fired = attachMovie("cannonball", "cannonball_"+_root.getNextHighestDepth(), _root.getNextHighestDepth(), {_x:start_ball_x, _y:start_ball_y});
    cannonball_fired.dirx = Math.cos(angle*Math.PI/180)*firepower;
    cannonball_fired.diry = Math.sin(angle*Math.PI/180)*firepower;
    cannonball_fired.onEnterFrame = function() {
        this.diry += gravity;
        this._x += this.dirx/30;
        this._y += this.diry/30;
        if ((this._x<0) or (this._x>500) or (this._y>350)) {
            this.removeMovieClip();
        }
    };
}

效果（速度明显变快了）：

然后再继续完善，设置同一时间开火的次数。

Mouse.hide();
gravity = 2;
fired = 0;
max_firepower = 3;
attachMovie("crosshair", "crosshair", 1);
attachMovie("tank", "tank", 2, {_x:230, _y:350});
crosshair.onEnterFrame = function() {
    this._x = _xmouse;
    this._y = _ymouse;
};
tank.onEnterFrame = function() {
    mousex = _xmouse-this._x;
    mousey = (_ymouse-this._y)*-1;
    angle = Math.atan(mousey/mousex)/(Math.PI/180);
    if (mousex<0) {
        angle += 180;
    }
    if (mousex>=0 && mousey<0) {
        angle += 360;
    }
    if (angle>160) {
        angle = 160;
    }
    if (angle<20) {
        angle = 20;
    }
    firepower = Math.sqrt(mousex*mousex+mousey*mousey);
    if (firepower>200) {
        firepower = 200;
    }
    this.cannon._rotation = angle*-1;
};
function onMouseDown() {
    if (fired         fired++;
        angle = tank.cannon._rotation-1;
        start_ball_x = tank._x+48*Math.cos(angle*Math.PI/180);
        start_ball_y = tank._y+48*Math.sin(angle*Math.PI/180);
        cannonball_fired = attachMovie("cannonball", "cannonball_"+_root.getNextHighestDepth(), _root.getNextHighestDepth(), {_x:start_ball_x, _y:start_ball_y});
        cannonball_fired.dirx = Math.cos(angle*Math.PI/180)*firepower;
        cannonball_fired.diry = Math.sin(angle*Math.PI/180)*firepower;
        cannonball_fired.onEnterFrame = function() {
            this.diry += gravity;
            this._x += this.dirx/30;
            this._y += this.diry/30;
            if (this._y>350) {
                this.removeMovieClip();
                fired--;
            }
        };
    }
}

效果（你这时连续按鼠标试试！）

在舞台上加上一个地面。

Mouse.hide();
gravity = 2;
fired = 0;
max_firepower = 3;
attachMovie("crosshair", "crosshair", 1);
attachMovie("tank", "tank", 2, {_x:295, _y:255});
attachMovie("ground", "ground", 3, {_x:0, _y:200});
crosshair.onEnterFrame = function() {
    this._x = _xmouse;
    this._y = _ymouse;
};
tank.onEnterFrame = function() {
    mousex = _xmouse-this._x;
    mousey = (_ymouse-this._y)*-1;
    angle = Math.atan(mousey/mousex)/(Math.PI/180);
    if (mousex<0) {
        angle += 180;
    }
    if (mousex>=0 && mousey<0) {
        angle += 360;
    }
    if (angle>160) {
        angle = 160;
    }
    if (angle<20) {
        angle = 20;
    }
    firepower = Math.sqrt(mousex*mousex+mousey*mousey);
    if (firepower>200) {
        firepower = 200;
    }
    this.cannon._rotation = angle*-1;
};
function onMouseDown() {
    if (fired         fired++;
        angle = tank.cannon._rotation-1;
        start_ball_x = tank._x+48*Math.cos(angle*Math.PI/180);
        start_ball_y = tank._y+48*Math.sin(angle*Math.PI/180);
        cannonball_fired = attachMovie("cannonball", "cannonball_"+_root.getNextHighestDepth(), _root.getNextHighestDepth(), {_x:start_ball_x, _y:start_ball_y});
        cannonball_fired.dirx = Math.cos(angle*Math.PI/180)*firepower;
        cannonball_fired.diry = Math.sin(angle*Math.PI/180)*firepower;
        cannonball_fired.onEnterFrame = function() {
            this.diry += gravity;
            this._x += this.dirx/30;
            this._y += this.diry/30;
            if ((this._y>350) or (ground.hitTest(this._x, this._y, true))) {
                this.removeMovieClip();
                fired--;
            }
        };
    }
}

效果如下：

然后再加上一个敌人。

Mouse.hide();
gravity = 2;
fired = 0;
max_firepower = 3;
place_enemy();
attachMovie("crosshair", "crosshair", 1);
attachMovie("tank", "tank", 2, {_x:295, _y:255});
attachMovie("ground", "ground", 3, {_x:0, _y:200});
crosshair.onEnterFrame = function() {
    this._x = _xmouse;
    this._y = _ymouse;
};
tank.onEnterFrame = function() {
    mousex = _xmouse-this._x;
    mousey = (_ymouse-this._y)*-1;
    angle = Math.atan(mousey/mousex)/(Math.PI/180);
    if (mousex<0) {
        angle += 180;
    }
    if (mousex>=0 && mousey<0) {
        angle += 360;
    }
    if (angle>160) {
        angle = 160;
    }
    if (angle<20) {
        angle = 20;
    }
    firepower = Math.sqrt(mousex*mousex+mousey*mousey);
    if (firepower>200) {
        firepower = 200;
    }
    this.cannon._rotation = angle*-1;
};
function onMouseDown() {
    if (fired         fired++;
        angle = tank.cannon._rotation-1;
        start_ball_x = tank._x+48*Math.cos(angle*Math.PI/180);
        start_ball_y = tank._y+48*Math.sin(angle*Math.PI/180);
        cannonball_fired = attachMovie("cannonball", "cannonball_"+_root.getNextHighestDepth(), _root.getNextHighestDepth(), {_x:start_ball_x, _y:start_ball_y});
        cannonball_fired.dirx = Math.cos(angle*Math.PI/180)*firepower;
        cannonball_fired.diry = Math.sin(angle*Math.PI/180)*firepower;
        cannonball_fired.onEnterFrame = function() {
            this.diry += gravity;
            this._x += this.dirx/30;
            this._y += this.diry/30;
            if ((this._y>350) or (ground.hitTest(this._x, this._y, true))) {
                this.removeMovieClip();
                fired--;
            }
        };
    }
}
function place_enemy() {
    enemy_placed = attachMovie("enemy", "enemy", _root.getNextHighestDepth(), {_x:0, _y:350});
    enemy_placed.yspeed = 0;
    enemy_placed.onEnterFrame = function() {
        this.yspeed += gravity/10;
        this._x++;
        while (_root.ground.hitTest(this._x+this._width/2, this._y+this._height, true)) {
            this._y--;
            this.yspeed = 0;
        }
        if (!_root.ground.hitTest(this._x+this._width/2, this._y+this._height+1, true)) {
            this._y += this.yspeed;
        } else {
            this.yspeed = 0;
        }
        if (this._x>500) {
            this.removeMovieClip();
            place_enemy();
        }
    };
}

效果如下：

最后完成。

Mouse.hide();
gravity = 2;
fired = 0;
max_firepower = 3;
place_enemy();
attachMovie("crosshair", "crosshair", 1);
attachMovie("tank", "tank", 2, {_x:295, _y:255});
attachMovie("ground", "ground", 3, {_x:0, _y:200});
crosshair.onEnterFrame = function() {
    this._x = _xmouse;
    this._y = _ymouse;
};
tank.onEnterFrame = function() {
    mousex = _xmouse-this._x;
    mousey = (_ymouse-this._y)*-1;
    angle = Math.atan(mousey/mousex)/(Math.PI/180);
    if (mousex<0) {
        angle += 180;
    }
    if (mousex>=0 && mousey<0) {
        angle += 360;
    }
    if (angle>160) {
        angle = 160;
    }
    if (angle<20) {
        angle = 20;
    }
    firepower = Math.sqrt(mousex*mousex+mousey*mousey);
    if (firepower>200) {
        firepower = 200;
    }
    this.cannon._rotation = angle*-1;
};
function onMouseDown() {
    if (fired         fired++;
        angle = tank.cannon._rotation-1;
        start_ball_x = tank._x+48*Math.cos(angle*Math.PI/180);
        start_ball_y = tank._y+48*Math.sin(angle*Math.PI/180);
        cannonball_fired = attachMovie("cannonball", "cannonball_"+_root.getNextHighestDepth(), _root.getNextHighestDepth(), {_x:start_ball_x, _y:start_ball_y});
        cannonball_fired.dirx = Math.cos(angle*Math.PI/180)*firepower;
        cannonball_fired.diry = Math.sin(angle*Math.PI/180)*firepower;
        cannonball_fired.onEnterFrame = function() {
            this.diry += gravity;
            this._x += this.dirx/30;
            this._y += this.diry/30;
            if ((this._y>350) or (ground.hitTest(this._x, this._y, true))) {
                this.removeMovieClip();
                fired--;
            }
            if (enemy.hitTest(this._x, this._y, true)) {
                this.removeMovieClip();
                enemy.removeMovieClip();
                fired--;
                place_enemy();
            }
        };
    }
}
function place_enemy() {
    enemy_placed = attachMovie("enemy", "enemy", _root.getNextHighestDepth(), {_x:0, _y:350});
    enemy_placed.yspeed = 0;
    enemy_placed.onEnterFrame = function() {
        this.yspeed += gravity/10;
        this._x++;
        while (_root.ground.hitTest(this._x+this._width/2, this._y+this._height, true)) {
            this._y--;
            this.yspeed = 0;
        }
        if (!_root.ground.hitTest(this._x+this._width/2, this._y+this._height+1, true)) {
            this._y += this.yspeed;
        } else {
            this.yspeed = 0;
        }
        if (this._x>500) {
            this.removeMovieClip();
            place_enemy();
        }
    };
}

最终简单游戏：

本教程中所用到所有源文件下载：点击这里下载源文件