制作一款打飞机游戏教程5：添加子弹

在上一篇中，我们设计了一个原型来测试飞船的移动和射击感觉。

我们注意到飞船在左右转向时的动画响应不一致。通过调整动画的中心值和范围，我们解决了这个问题，使得飞船在左右转向时的动画响应更加对称和一致。

为了简化代码并提高可读性，我们使用了三元运算符来替换一些冗长的if-else语句。虽然这次优化节省的不多，但它使代码更加紧凑和易于维护。

接下来，我们开始实现射击功能。首先，我们设计了一个简单的子弹精灵，并编写了代码来控制子弹的发射和移动。

我们通过在按下射击键时创建一个新的子弹对象，并将其添加到子弹数组中来实现子弹的发射。然后，在更新函数中遍历子弹数组，更新每个子弹的位置。

为了避免子弹发射过快导致的视觉混乱，我们实现了一个射击频率控制机制。通过设置子弹的发射间隔，我们可以控制子弹的发射速度，使其看起来更加合理。

为了增强游戏的视觉效果和玩家反馈，我们计划添加一些特效，如枪口火焰和爆炸效果。

我们设计了一个简单的枪口火焰动画，并将其与射击动作同步播放。这样，当玩家按下射击键时，不仅能看到子弹射出，还能看到枪口冒出的火焰，增强了射击的真实感。

pico-8 cartridge // http://www.pico-8.com
version 41
__lua__
-- t: make basic movement feel nice
--    ❎: fixed cobblestoning
--    ❎: what is a good movement speed
--    t: do banking-- t: make shooting feel nice!-- x: normalized diagonalsbutarr={1,2,0,3,5,6,3,4,8,7,4,0,1,2,0}dirx={-1,1, 0,0, -0.7, 0.7,0.7,-0.7}
diry={ 0,0,-1,1, -0.7,-0.7,0.7,0.7}butarr[0]=0shiparr={1,3,5,7,9}shipspr=0shots={}
shotwait=0function _init()px,py=64,64spd=1.4lastdir=0cls(0)
endfunction _draw()cls(12)spr(shiparr[flr(shipspr*2.4+3.5)],px,py,2,2)--pset(px,py,8)for s in all(shots) dospr(11,s.x,s.y)endlocal btnv=btn()&0b1111print(btn(),5,5,7)print(btnv,5,11,7)print(butarr[btnv],5,17,7)print(shotwait,5,23,7)
endfunction _update60()local dir=butarr[btn()&0b1111]if lastdir!=dir and dir>=5 then--anti-cobblestonepx=flr(px)+0.5py=flr(py)+0.5endlocal dshipspr=0if dir>0 thenpx+=dirx[dir]*spdpy+=diry[dir]*spddshipspr=mysgn(dirx[dir])endshipspr+=mysgn(dshipspr-shipspr)*0.15shipspr=mid(-1,shipspr,1)lastdir=dirif shotwait>0 thenshotwait-=1endif btn(❎) thenif shotwait<=0 thenadd(shots,{x=px,y=py,sx=0,sy=-1})shotwait=7endenddoshots()
endfunction doshots()for s in all(shots) dos.x+=s.sxs.y+=s.syend
endfunction mysgn(v) return v==0 and 0 or sgn(v)
end
__gfx__
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