Lunar Lander - Tap to Burn - MATLAB One-Button Game Mini Hack

Shuen
/
Lunar Lander - Tap to Burn
on 2 Nov 2026
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game.m
function g = game()
%game ONE-BUTTON LUNAR LANDER - tap SPACE (or click) to toggle the engine.
% Physics: 1-D vertical descent in lunar gravity, variable mass (rocket
% equation), first-order engine spool lag. Touch down below 3 m/s.
% Tip: hovering wastes fuel (gravity loss = g*t_burn). The fuel-optimal
% landing is: coast, then ONE late full-thrust burn ("suicide burn"):
% tap ON when the HUD turns red, tap OFF just before touchdown.
%
%   >> minihackContest.validate   % check the contract and contest rules
%   >> minihackContest.play       % play locally at 30 fps
%   >> minihackContest.submit     % publish to the contest

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

function s = initState(ax)
%% Vehicle & environment (SI) - legacy-lander flavoured, scaled for a short game
s.g   = 1.62;      % lunar surface gravity [m/s^2]
s.g0  = 9.80665;   % standard gravity (Isp definition) [m/s^2]
s.Isp = 311;       % descent engine specific impulse [s]
s.Tmx = 16e3;      % thrust, on/off engine [N]
s.mD  = 4000;      % dry mass [kg]
s.F0  = 200;       % propellant at start [kg]  (160 = hard mode)
s.tau = 0.25;      % engine spool time constant [s]
s.h   = 0.005;     % physics substep [s]
s.Y0  = 500;       % start altitude [m]
s.V0  = -10;       % start vertical speed [m/s] (negative = down)
s.Vok = 3;         % touchdown limit [m/s]

%% Pixel canvas & palette
W = 160; H = 120; G = 104;              % canvas size, landing-surface row
s.G = G;
pal = [0 0 0; .78 .78 .82; .42 .42 .48; .96 .76 .22; .66 .48 .10; ...
       .08 .10 .25; 1 1 1; 1 .50 .10; 1 .92 .35; .90 .15 .10; ...
       .55 .55 .52; .35 .35 .33; .20 .45 .90; .25 .70 .35; .45 .45 .50; ...
       .07 .03 .15; .14 .05 .26; .24 .08 .38; .45 .75 1; .17 .15 .24; ...
       .26 .23 .34; .06 .15 .40; .92 .95 1; .15 .15 .15; .20 1 .40];
% 1 space 2 hull 3 frame 4 foil 5 foil-dk 6 window 7 white 8 flame-o
% 9 flame-y 10 red 11 regolith 12 regolith-dk 13 ocean 14 land 15 dim star
% 16-18 nebula (dark->bright) 19 atmosphere 20 ridge 21 ridge-hi
% 22 night ocean 23 cloud/ice 24 pad-dark 25 green beacon

rng(7);                                 % fixed scenery every run
[xx,yy] = meshgrid(1:W,1:H);
B = ones(H,W);
% Purple nebula: layered sines + dither, brighter toward the core
n = sin(xx/11+yy/7) + .7*sin(xx/6.5-yy/9) + .5*sin((xx-yy)/4.3) + .6*rand(H,W);
B(n > 1.1) = 16;  B(n > 1.6) = 17;  B(n > 2.0) = 18;
B(yy > G-34 & rand(H,W) < (yy-G+34)/40) = 16;            % horizon glow
B(rand(H,W)<.010) = 15;  B(rand(H,W)<.004) = 7;          % stars
for p = [24 30; 52 12; 112 44; 148 70; 8 60]'            % four-point sparkles
  B(p(2)-1:p(2)+1,p(1)) = 15;  B(p(2),p(1)-1:p(1)+1) = 15;  B(p(2),p(1)) = 7;
end
% Earth: atmosphere rim, oceans/continents, clouds, ice cap, night side
d2 = (xx-132).^2+(yy-22).^2;  e = d2 <= 49;
B(d2 <= 66 & ~e) = 19;  B(e) = 13;  B(e & rand(H,W)<.35) = 14;
B(e & rand(H,W)<.12) = 23;  B(e & yy < 17) = 23;
nt = e & (xx-132) + .4*(yy-22) > 2;  B(nt & B==13) = 22;  B(nt & B~=22) = 20;
% Distant ridge, then foreground regolith with a flat zone under the lander
x = 1:W;  top = G+0*x;  o = abs(x-80) > 14;
top(o) = G - round(2+2*sin(x(o)/6)+sin(x(o)/2.3));
rr = G - 14 - round(4*sin(x/13)+2.5*sin(x/5.3)+1.5*sin(x/2.1));
for c = 1:W, B(rr(c):top(c),c) = 20;  B(rr(c),c) = 21;  B(top(c)+1:H,c) = 11; end
B(B==11 & rand(H,W)<.25) = 12;                           % regolith texture
for k = 1:7                                              % craters
  cx = randi(W); cy = G+4+randi(12); r = 1+randi(3);
  B((xx-cx).^2+4*(yy-cy).^2 <= r^2 & yy > G+1) = 12;
end
B(G+1,68:92) = 9 + 15*(mod(68:92,4) < 2);  B(G+2,68:92) = 3;   % hazard-stripe pad
s.tw = find(B==7 | B==15);  s.ph = 6.3*rand(size(s.tw));  % twinkle set + phases
s.B = B;

% Generic legacy-style lander: crew cabin on a foil-wrapped descent stage
S = ['......333......'
     '.....32223.....'
     '....3262623....'
     '....3222223....'
     '...333333333...'
     '...454545454...'
     '...544444445...'
     '...454545454...'
     '...333333333...'
     '..3...333...3..'
     '.3...........3.'
     '3.............3'
     '77...........77'];
s.M = S ~= '.';  s.P = double(S) - 48;

%% Axes look + graphics (created once; render only mutates them)
ax.XLim = [.5 W+.5];  ax.YLim = [.5 H+.5];  ax.YDir = 'reverse';
ax.Color = 'k';  colormap(ax,pal);
o = {'HitTest','off','PickableParts','none'};
s.im  = image(ax,'CData',B,'CDataMapping','direct',o{:});
s.hud = text(ax,4,4,'','Color',[.35 1 1],'FontName','Courier','FontSize',10, ...
             'FontWeight','bold','VerticalAlignment','top',o{:});
s.msg = text(ax,80,62,'','Color',[1 .92 .35],'FontName','Courier', ...
             'FontSize',13,'FontWeight','bold','HorizontalAlignment','center', ...
             'BackgroundColor',[.06 .02 .14],'EdgeColor',[.80 .30 1], ...
             'LineWidth',1.5,'Margin',6,o{:});

% Title: dim-purple halo (4 offset copies) under a bright neon core
for d = [-.4 -.4; .4 -.4; -.4 .4; .4 .4; 0 0]'
  text(ax,80+d(1),1.5+d(2),'LUNARLANDER','Color',[.80 .30 1]-[.35 .20 .25]*any(d), ...
       'FontName','Courier','FontSize',18,'FontWeight','bold', ...
       'HorizontalAlignment','center','VerticalAlignment','top',o{:});
end

%% Game state
s.st = 0;                               % 0 title, 1 flight, 2 landed/crashed
s.t = 0;  s.best = 0;                   % animation clock, session best score
s = resetRound(s);
s.txt = sprintf('TAP = ENGINE ON / OFF\nLAND SOFT, SAVE FUEL\n> TAP TO START <');
s.C = drawScene(s);
end

function s = updateState(s, dt, pressed)
% Fixed-step physics driven by the harness dt; engine is tap-toggled.
s.t = s.t + dt;
if s.st == 0                                        % title screen
  if pressed, s.st = 1; s.txt = ''; end
elseif s.st == 1                                    % flight
  if pressed && s.F > 0, s.eng = ~s.eng; end      % tap = toggle engine
  s.acc = s.acc + dt;  n = floor(s.acc/s.h);  s.acc = s.acc - n*s.h;
  y = s.y; v = s.v; F = s.F; T = s.T; h = s.h;
  for k = 1:n
    u = s.eng && F > 0;                           % engine command (on/off)
    T = T + (s.Tmx*u - T)*h/s.tau;                % spool lag
    m = s.mD + F;
    v = v + (T/m - s.g)*h;                        % semi-implicit Euler
    y = y + v*h;
    F = max(F - T/(s.Isp*s.g0)*h, 0);             % mass flow = T/(Isp*g0)
    if y <= 0 || y > 1.5*s.Y0, s.st = 2; break; end
  end
  if F <= 0, s.eng = false; end                   % flame-out
  if s.st == 2                                    % touchdown / abort
    vt = -v;  y = max(y,0);  s.crash = vt >= s.Vok;
    if y > 0,          r = 'ABORT: CLIMBED OUT'; s.crash = false;
    elseif vt < 1,     r = '* PERFECT TOUCHDOWN *';
    elseif vt < 2,     r = 'GOOD LANDING';
    elseif vt < s.Vok, r = 'HARD LANDING';
    else,              r = 'CRASHED';
    end
    sc = round(10*F*(vt<s.Vok)*(1+(vt<1))*(y==0));
    s.best = max(s.best, sc);
    s.txt = sprintf('%s\n%.2f m/s  FUEL %.0f kg\nSCORE %d   BEST %d\n> TAP TO RETRY <', ...
                    r,vt,F,sc,s.best);
    T = 0;  s.eng = false;
  end
  s.y = y; s.v = v; s.F = F; s.T = T;
elseif pressed                                      % retry
  s = resetRound(s);  s.st = 1;
end
s.C = drawScene(s);   % all randomness lives here, so render stays idempotent
end

function renderFrame(~, s)
% Only mutate existing handles. HUD: rocket equation + burn-now cue.
m  = s.mD + s.F;  aB = s.Tmx/m - s.g;               % net decel at full thrust
dS = (s.v<0)*(s.v^2/(2*aB)) + abs(s.v)*s.tau;       % stopping distance incl. lag
dV = s.Isp*s.g0*log(m/s.mD);                        % remaining delta-v
e  = {'OFF','ON'};
s.hud.String = sprintf(['ALT %6.1f m\nV/S %6.1f m/s\nFUEL%6.1f kg\n' ...
    'dV  %6.1f m/s\nT/W %6.2f\nENG %s'], s.y, s.v, s.F, dV, s.T/(m*s.g), e{1+s.eng});
burn = s.st==1 && s.y < 1.05*dS;                    % red = burn now
s.hud.Color = [.35 1 1] + [.65 -.75 -.75]*burn;
s.msg.String = s.txt;
s.msg.Visible = ~isempty(s.txt);
s.im.CData = s.C;
end

function C = drawScene(s)
% Compose the pixel frame: background + twinkle/beacons + lander + flame/debris.
C = s.B;  G = s.G;  W = size(C,2);  H = size(C,1);  t = s.t;
C(s.tw) = 15 - 8*(sin(3*t + s.ph) > .3);            % twinkling stars
C(G,67) = 20 - 10*(mod(t,1) < .5);                  % blinking pad beacons
C(G,93) = 20 + 5*(mod(t,1) >= .5);
F = s.F/s.F0;                                       % fuel gauge under HUD
C(23:24,4:43) = 20;  C(23:24,4:3+round(40*F)) = 25 - 15*(F < .25);
y = s.y;  T = s.T;
if s.st == 0                                        % attract mode: hover + burn
  y = .82*s.Y0 + 25*sin(2*t);  T = .8*s.Tmx;
end
yb = G - round(min(y,s.Y0)/s.Y0*(G-25));            % sprite bottom row
if s.crash                                          % debris
  n = 50;
  C(sub2ind([H W], G-randi(10,1,n), 80+randi([-12 12],1,n))) = randi([8 10],1,n);
else
  R = C(yb-12:yb,73:87);  R(s.M) = s.P(s.M);  C(yb-12:yb,73:87) = R;
  L = round(T/s.Tmx*(5+2*rand));                    % flame length [px]
  for k = 1:L
    q = yb-2+k;  w = max(0,1-floor(k/3));
    if q <= G, C(q,80-w:80+w) = 9-(k>2)+2*(k>5);  C(q,80) = 7+2*(k>2); end
  end
  if T > .2*s.Tmx && y < 20                         % plume kicks up regolith
    n = round(14*(1-y/20));
    C(sub2ind([H W], G-randi(2,1,n), 80+(2*(rand(1,n)>.5)-1).*randi([5 24],1,n))) = 11;
  end
end
end

function s = resetRound(s)
% Reset numeric state; preserve graphics handles and best score.
s.y = s.Y0; s.v = s.V0; s.F = s.F0; s.T = 0;
s.crash = false; s.eng = false; s.acc = 0; s.txt = '';
end
Play Game
Preview

Play Game opens this in MATLAB Drive. Click Run this app there to play.