Space Bar Invaders

Claudia
/
Space Bar Invaders
on 3 Nov 2026
4
11
6
0
9712
game.m
function g = game()
%game Space Invaders -- one-button edition.
%
%   Your cannon patrols the ground on its own, bouncing off the edges.
%   SPACE is the only input: each tap turns the cannon around to dodge
%   incoming fire or chase a target. The cannon fires on its own (one
%   shot on screen at a time, like the arcade) except under a bunker.
%
%       >> minihackContest.validate
%       >> minihackContest.play

g.init = @initState;
g.update = @updateState;
g.render = @renderFrame;
end

function s = initState(ax)
set(ax,'YDir','reverse','Color','k','XLim',[0 800],'YLim',[0 600]);
P={'HitTest','off','PickableParts','none'};

% Pixel sprites, 8 rows x 16 bits each, as hex. 1-2 squid, 3-4 crab,
% 5-6 octopus, 7 UFO, 8 cannon, 9 alien explosion, 10 cannon explosion.
B=dec2bin(hex2dec(reshape(['18003C007E00DB00FF0024005A00A50018003C007E00DB00FF005A0081004200' ...
  '208011003F806EC0FFE0BFA0A0A01B0020809120BFA0EEE0FFE07FC0208040400F007FE0FFF0E670FFF0' ...
  '198036C0C0300F007FE0FFF0E670FFF039C0666030C007E01FF83FFC6DB6FFFF399C100800000200070007' ...
  '007FF0FFF8FFF8FFF8FFF80880451020201040C01810402520489004004120120005402F004FD03FE07FF0'  ],4,[])'),16)=='1';
for k=1:10
    [r,c]=find(B(8*k-7:8*k,:));
    s.SX{k}=3*c-3; s.SY{k}=3*r-3; s.W(k,1)=3*max(c);
end
s.SX{12}=0; s.SY{12}=0;                             % single pixel
s.SX{13}=[0;0;0;0]; s.SY{13}=[0;3;6;9];             % player shot
s.rt=[1;2;2;3;3];                                   % sprite type per row
s.rc=[1 .3 .8;.6 .5 1;.3 .85 1;.3 1 .5;.9 1 .3];    % colour per row
G=[.2 1 .3];

% Bunker: rounded top corners, arch cut out of the bottom
[X,Y]=meshgrid(1:22,1:16);
s.M=~(X+Y<6 | 23-X+Y<6 | ((X-11.5)/5).^2+((Y-17)/7).^2<1);

% Twinkling starfield + ground
s.sp=6.3*rand(90,1); s.sw=1+3*rand(90,1);
s.st=scatter(ax,800*rand(90,1),550*rand(90,1),4+10*rand(90,1),ones(90,3),'filled',P{:});
line(ax,[0 800],[562 562],'Color',G,'LineWidth',2,P{:});

% Patches: bunkers, aliens, UFO, cannon, explosions, lives, title table
C={G,'flat',[1 .2 .25],G,'flat',G,'flat'};
for k=1:7
    s.h(k)=patch(ax,'XData',NaN,'YData',NaN,'FaceColor',C{k},'EdgeColor','none',P{:});
end
s.hAB=line(ax,NaN,NaN,'Color',[1 .8 .4],'LineWidth',2,P{:});

% Texts: header, message, sub-message, then the title screen.
L={'','','','SPACE INVADERS','*SCORE ADVANCE TABLE*', ...
   '= ? MYSTERY','= 30 POINTS','= 20 POINTS','= 10 POINTS'};
X=400+40*((1:9)>5);
Y=[22 300 345 130 230 290 340 390 440];
Z=[16 32 15 46 16 16 16 16 16];
for k=1:9
    s.tx(k)=text(ax,X(k),Y(k),L{k},'Color','w','FontSize',Z(k),'FontName','Courier', ...
        'FontWeight','bold','HorizontalAlignment','center',P{:});
end
set(s.tx([3 4]),'Color',G);

K=[7;1;3;5];
q(s.h(7),s,K,330-s.W(K)/2,Y(6:9)'-11,[1 .2 .25;s.rc([1 3 5],:)],1,3);

s.hi=0; s.t=0; s.wave=1;
s=newWave(s);
s.mode=0;   % 0 title, 1 play, 2 dying, 3 game over, 4 get ready
end

function s = updateState(s,dt,pressed)
s.t=s.t+dt; s.tm=s.tm+dt;
s.ex(:,3)=s.ex(:,3)-dt;
s.ex(s.ex(:,3)<=0,:)=[];
m=s.mode;
if pressed && (m==0 || m==3 && s.tm>1)
    s.wave=1; s=newWave(s); s.mode=4;
end
if m==4 && s.tm>1.5, s.mode=1; end
if m==2 && s.tm>1.6
    s.tm=0; s.px=380; s.mode=1+2*(s.lives<1);
end
if m~=1, return; end

% Cannon patrols on its own and SPACE turns it around. It fires
% automatically whenever its shot is free, unless a bunker is overhead.
s.pd=s.pd*(1-2*pressed);
if ~s.bOn && ~any(s.G(:,floor(s.px/3+7.5)))
    s.bOn=true; s.bx=s.px+19.5; s.by=522;
end
s.px=s.px+s.pd*210*dt;
if s.px<10 || s.px>751
    s.pd=-s.pd; s.px=min(max(s.px,10),751);
end

% Player shot, swept between y1 (top) and y0
if s.bOn
    y0=s.by+12; s.by=s.by-650*dt; y1=s.by;
    [X,Y,w,r,c]=alienPos(s);
    h=find(s.bx>=X & s.bx<=X+w & y1<=Y+24 & y0>=Y);
    [b,s.G]=bunk(s.G,s.bx,y1,y0,-1);
    a=abs(s.ab(:,1)-s.bx)<6 & s.ab(:,2)<=y0 & s.ab(:,2)+15>=y1;
    if y1<40 || b
        s.bOn=false;
    elseif ~isempty(h)
        [~,j]=max(Y(h)); k=h(j);
        s.alive(r(k),c(k))=false;
        s.score=s.score+40-10*s.rt(r(k));
        s=boom(s,X(k)+w(k)/2,Y(k)+12,.3,s.rc(r(k),:));
    elseif s.uOn && abs(s.bx-s.ux-24)<24 && y1<=81 && y0>=60
        v=50*randi(6);
        s.score=s.score+v;
        s=boom(s,s.ux+24,70,.4,[1 .2 .25]);
        s.uOn=false;
    elseif any(a)
        s.ab(a,:)=[];
        s=boom(s,s.bx,y1,.15,[1 1 1]);
    end
end

% Formation marches in steps; fewer aliens => faster
n=nnz(s.alive);
if n==0
    s.wave=s.wave+1; s=newWave(s); s.mode=4;
    return
end
iv=max(.016,.012*n)/(1+.15*(s.wave-1));
s.stepT=s.stepT+dt;
if s.stepT>=iv
    s.stepT=0;
    s.frame=1-s.frame;
    [X,~,w]=alienPos(s);
    e=(s.fd>0 && max(X+w)>782) || (s.fd<0 && min(X)<18);
    s.fy=s.fy+16*e; s.fx=s.fx+8*s.fd*~e; s.fd=s.fd*(1-2*e);
end

% Low aliens crush the bunkers; reaching the ground ends it
[~,Y]=alienPos(s);
s.G(1:min(16,ceil(max(Y)/3)-142),:)=false;
if any(Y>=501)
    s.lives=1; s=die(s);
    return
end

% Aliens fire from the bottom of a random column
s.fireT=s.fireT-dt;
if s.fireT<=0 && size(s.ab,1)<min(6,2+s.wave)
    s.fireT=max(.25,1.1-.1*s.wave)*(.5+rand);
    c=find(any(s.alive,1));
    c=c(randi(numel(c)));
    s.ab(end+1,:)=[s.fx+c*48-30, s.fy+find(s.alive(:,c),1,'last')*40-16, randi(2)];
end
y0=s.ab(:,2);
s.ab(:,2)=y0+(200+15*s.wave)*dt;
k=s.ab(:,2)>545;
for i=1:numel(y0)
    [b,s.G]=bunk(s.G,s.ab(i,1),y0(i),s.ab(i,2)+15,1);
    k(i)=k(i)||b;
end
if any(~k & abs(s.ab(:,1)-s.px-19.5)<19 & abs(s.ab(:,2)-531)<18)
    s=die(s);
    return
end
s.ab(k,:)=[];

% Mystery ship
s.uT=s.uT-dt;
s.ux=s.ux+s.ud*130*dt;
s.uOn=s.uOn && abs(s.ux-400)<460;
if ~s.uOn && s.uT<=0 && n>=8
    s.uOn=true; s.ud=2*(rand>.5)-1;
    s.ux=400-450*s.ud; s.uT=18+10*rand;
end
s.hi=max(s.hi,s.score);
end

function renderFrame(~,s)
on=s.mode~=0;
s.st.CData=(.25+.6*abs(sin(s.t*s.sw+s.sp))).*[.8 .85 1];

% Aliens, bunkers, UFO, cannon, explosions, reserve lives
[X,Y,~,r]=alienPos(s);
q(s.h(2),s,2*s.rt(r)-1+s.frame,X,Y,s.rc(r,:),on,3);
[r,c]=find(s.G);
q(s.h(1),s,12,3*c-3,3*r+447,[],on,3);
q(s.h(3),s,7,s.ux,60,[],s.uOn&&on,3);
q(s.h(4),s,[8+2*(s.mode==2)*mod(floor(s.tm*8),2);13],[s.px;s.bx-1.5-9e3*~s.bOn],[525;s.by],[],any(s.mode==[1 2 4]),3);
q(s.h(5),s,9,s.ex(:,1)-19.5,s.ex(:,2)-12,s.ex(:,4:6),on,3);
n=(1:s.lives-1)';
q(s.h(6),s,8,50*n-5,574+0*n,[],on,2);

% Alien shots: zig-zags and plungers with a travelling cross-bar
a=s.ab;
p=1-2*mod(floor(s.t*12)+(1:size(a,1))',2);
t=a(:,3)==1;
y=3+4*mod(floor(s.t*16),3);
bx=a(:,1)+t.*p.*[-3 3 -3 3 -3]+~t.*[0 0 0 -4 4];
by=a(:,2)+t.*[0 4 8 12 15]+~t.*[0 15 y y y];
bx(:,6)=NaN; by(:,6)=NaN; bx=bx'; by=by';
set(s.hAB,'XData',bx(:),'YData',by(:),'Visible',on);

% HUD, messages and title screen
M={'','','','GAME OVER','WAVE '+string(s.wave)};
M2={'TAP SPACE TO TURN - AUTO-FIRE','','','PRESS SPACE TO REPLAY','GET READY'};
b=mod(s.t,1)<.6 || s.mode>3;
set(s.tx(1:3),{'String'},{sprintf('SCORE %05d    HI-SCORE %05d    WAVE %d',s.score,s.hi,s.wave); ...
    M{s.mode+1};M2{s.mode+1}});
set(s.tx(3),'Position',[400 345+160*~on 0],'Visible',b && (s.mode~=3 || s.tm>1));
set([s.tx(4:9) s.h(7)],'Visible',~on);
end

function s = newWave(s)
if s.wave<2, s.score=0; s.lives=3; end
s.alive=true(5,11);
s.fx=142; s.fy=100+16*min(s.wave-1,6); s.fd=1;
s.frame=0; s.stepT=0; s.fireT=1.5; s.tm=0;
s.ab=zeros(0,3); s.ex=zeros(0,6);
s.bOn=false; s.bx=0; s.by=0; s.px=380; s.pd=1;
s.uOn=false; s.ux=0; s.ud=1; s.uT=20;
s.G=[zeros(16,42) repmat([s.M zeros(16,31)],1,4) zeros(16,13)]>0;
end

function s = die(s)
s.lives=s.lives-1; s.mode=2; s.tm=0;
s.ab=zeros(0,3); s.bOn=false;
end

function s = boom(s,x,y,t,c)
% Spawn an explosion and retire the player's shot.
s.ex(end+1,:)=[x y t c];
s.bOn=false;
end

function [X,Y,w,r,c] = alienPos(s)
[r,c]=find(s.alive);
w=s.W(2*s.rt(r)-1);
X=s.fx+(c-1)*48+(36-w)/2;
Y=s.fy+(r-1)*40;
end

function [hit,G] = bunk(G,x,ya,yb,d)
% Swept test of a shot in column x from ya (top) to yb (bottom) against
% the bunker grid; d>0 = moving down. Blasts a ragged hole on impact.
c=floor(x/3)+1;
rr=max(1,floor(ya/3)-149):min(16,floor(yb/3)-149);
i=find(G(rr,c));
hit=~isempty(i);
if hit
    i=rr(i(1+(d<0)*(end-1)));
    R=max(i-3,1):min(i+3,16); C=max(c-2,1):min(c+2,267);
    G(R,C)=G(R,C) & rand(numel(R),numel(C))>.75;
end
end

function q(h,s,K,X,Y,C,v,z)
% Draw sprites K at top-left X,Y (pixel size z, optional per-sprite
% colours C) into an existing patch.
[x,y,c]=deal([]);
K=K+0*X;
for k=unique(K)'
    i=find(K==k); n=numel(s.SX{k});
    x=[x;reshape(X(i)'+s.SX{k}*z/3,[],1)]; %#ok<AGROW>
    y=[y;reshape(Y(i)'+s.SY{k}*z/3,[],1)]; %#ok<AGROW>
    if ~isempty(C), c=[c;C(repelem(i,n),:)]; end %#ok<AGROW>
end
n=numel(x);
if v && n
    set(h,'Vertices',[x y;x+z y;x+z y+z;x y+z],'Faces',(1:n)'+[0 n 2*n 3*n],'Visible','on');
    if n==size(c,1), h.FaceVertexCData=c; end
else
    h.Visible='off';
end
end
Play Game
Preview

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