Stay On Target: Trench Run

Josh Natanson
/
Stay On Target: Trench Run
on 2 Nov 2026
8
53
21
0
8608
game.m
function g = game()
%game Death Star trench run. Tap to thrust, dodge obstacles, hit the port.

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

function s = initState(ax)
ax.Color = 'k';
ax.XLim = [0 800];
ax.YLim = [0 600];

% World: floor y=0, rim y=H, walls x=+-W. Ship sits at z=0, camera behind.
s.H = 120;
s.W = 60;
s.h = 6;
s.grav = -260;
s.boost = 130;
s.camZ = 120;
s.f = 300;
s.far = 1500;

s.score = 0;
s.ob = struct('z', {}, 'k', {}, 'lo', {}, 'hi', {});
s.bz = struct('z', {}, 'x', {}, 'y', {}, 'v', {});
s = newStage(s, 1);
s.mode = 'title';
s.msg = 'DEATH STAR TRENCH RUN';

% Ship model (x, y, z offsets), NaN rows split polylines.
s.M = [-4 0 -8; 0 3 14; 4 0 -8; -4 0 -8; NaN NaN NaN
    -24 -5 -6; -4 0 -2; NaN NaN NaN; 24 -5 -6; 4 0 -2; NaN NaN NaN
    -24 5 -6; -4 0 -2; NaN NaN NaN; 24 5 -6; 4 0 -2];

s.g.st = line(ax, 800 * rand(120, 1), 340 + 260 * rand(120, 1), ...
    'LineStyle', 'none', 'Marker', '.', 'MarkerSize', 4, 'Color', 'w', ...
    'HitTest', 'off', 'PickableParts', 'none');
s.g.tr = mkLine(ax, [0.2 1 0.3]);
s.g.ob = mkLine(ax, [1 0.25 0.2]);
s.g.sh = mkLine(ax, [1 0.9 0.2]);
s.g.fx = mkLine(ax, [1 0.6 0.1]);
s.g.bl = mkLine(ax, [1 0.2 0.8]);
s.g.bl.LineWidth = 3;
s.g.hud = mkText(ax, 10, 580, 12, 'left');
s.g.msg = mkText(ax, 400, 360, 26, 'center');
s.g.sub = mkText(ax, 400, 320, 14, 'center');
end

function h = mkLine(ax, c)
h = line(ax, NaN, NaN, 'Color', c, 'LineWidth', 1.5, ...
    'HitTest', 'off', 'PickableParts', 'none');
end

function h = mkText(ax, x, y, sz, al)
h = text(ax, x, y, '', 'Color', 'w', 'FontSize', sz, ...
    'FontName', 'Courier', 'FontWeight', 'bold', ...
    'HorizontalAlignment', al, 'HitTest', 'off', 'PickableParts', 'none');
end

function s = updateState(s, dt, pressed)
s.t = s.t + dt;
switch s.mode
    case 'title'
        if pressed
            s.mode = 'play';
            s.t = 0;
            s.msg = '';
        end
    case 'play'
        if pressed
            s.vy = s.boost;
        end
        s.vy = s.vy + s.grav * dt;
        s.y = s.y + s.vy * dt;
        dz = s.v * dt;
        s.d = s.d + dz;
        s.score = s.score + dz / 10;
        s.camY = s.camY + (s.y + 40 - s.camY) * min(1, 4 * dt);
        hit = false;
        for i = 1:numel(s.ob)
            o = s.ob(i);
            z = o.z - dz;
            % Check on crossing, not equality, so high speed can't tunnel.
            % Upper slabs top out at the rim, so a ship above it clears them.
            hit = hit || (o.z > 0 && z <= 0 && (s.y - s.h < o.lo || ...
                (o.hi < s.H && s.y + s.h > o.hi && s.y - s.h < s.H)));
            s.ob(i).z = z;
        end
        s.ob = s.ob([s.ob.z] > -200);
        % Turbolaser bolts sweep over the rim; only an exposed ship gets hit.
        zap = false;
        for i = 1:numel(s.bz)
            b = s.bz(i);
            z = b.z + b.v * dt;
            zap = zap || (b.z * z <= 0 && s.y > s.H && abs(s.y - b.y) < 10 && abs(b.x) < 26);
            s.bz(i).z = z;
        end
        s.bz = s.bz([s.bz.z] > -s.camZ - 60 & [s.bz.z] < s.far + 10);
        s.nextBolt = s.nextBolt - dt;
        if s.nextBolt <= 0
            s = fire(s);
        end
        s.spark = max(0, s.spark - dt);
        s.nextZ = s.nextZ - dz;
        % Spawns appear s.far ahead; keep the run-up to the port clear.
        if s.nextZ <= 0 && s.d + s.far < s.L - 800
            s = spawn(s);
        end
        % Floor gives a small bounce; above the rim there's a soft ceiling.
        if s.y - s.h < 0
            s.y = s.h;
            s.vy = 120;
            s.score = max(0, s.score - 50);
            s.spark = 0.3;
        end
        if s.y > s.H + 40
            s.y = s.H + 40;
            s.vy = min(s.vy, 0);
        end
        if zap
            s = die(s, 'TURBOLASER FIRE!');
        elseif hit
            s = die(s, 'CRASH!');
        elseif s.d >= s.L
            if s.y < 35
                s.mode = 'win';
                s.t = 0;
                s.msg = 'DIRECT HIT!';
                s.score = s.score + 1000 * s.stage;
            else
                s = die(s, 'MISSED THE PORT!');
            end
        end
    case 'boom'
        if pressed && s.t > 1
            s.score = 0;
            s = newStage(s, 1);
        end
    case 'win'
        if pressed && s.t > 1
            s = newStage(s, s.stage + 1);
        end
end
end

function s = newStage(s, n)
s.stage = n;
s.v = 300 * min(1.15 ^ (n - 1), 2);
s.L = 6000 + 1500 * (n - 1);
s.d = 0;
s.ob = s.ob([]);
s.nextZ = 400;
s.bz = s.bz([]);
s.nextBolt = 1.5;
s.spark = 0;
s.y = 60;
s.vy = 0;
s.camY = 100;
s.mode = 'play';
s.t = 0;
s.msg = '';
end

function s = spawn(s)
% New obstacle at the far end; gaps shrink and spacing tightens per stage.
H = s.H;
gap = max(40, 80 - 6 * s.stage);
k = randi(3);
switch k
    case 1
        lo = 20 + rand * (H - gap - 20);
        hi = H;
    case 2
        lo = 0;
        hi = gap + rand * (H - 20 - gap);
    otherwise
        lo = 10 + rand * (H - gap - 20);
        hi = lo + gap;
end
s.ob(end + 1) = struct('z', s.far, 'k', k, 'lo', lo, 'hi', hi);
% At least 0.8 s between obstacles so any pair of gaps is reachable.
s.nextZ = max(s.nextZ, 0) + max(0.8 * s.v, max(250, 600 - 60 * s.stage) * (0.8 + 0.4 * rand));
end

function s = fire(s)
% Bolt from ahead (closing fast) or behind (overtaking), just over the rim.
if rand < 0.5
    z = s.far;
    v = -(s.v + 600);
else
    z = -s.camZ - 30;
    v = 500;
end
s.bz(end + 1) = struct('z', z, 'x', 70 * rand - 35, 'y', s.H + 5 + 30 * rand, 'v', v);
s.nextBolt = (0.5 + rand) / (1 + 0.1 * (s.stage - 1));
end

function s = die(s, why)
s.mode = 'boom';
s.t = 0;
s.msg = why;
end

function renderFrame(~, s)
W = s.W;
H = s.H;
z0 = 20 - s.camZ;
% Rails along the floor edges and rim.
P = [-W 0 z0; -W 0 s.far; NaN NaN NaN; W 0 z0; W 0 s.far; NaN NaN NaN
    -W H z0; -W H s.far; NaN NaN NaN; W H z0; W H s.far; NaN NaN NaN];
% Cross ribs scroll with distance to sell speed.
for z = 100 - mod(s.d, 100) + (-100:100:s.far - 100)
    P = [P; -W H z; -W 0 z; W 0 z; W H z; NaN NaN NaN]; %#ok<AGROW>
end
setXY(s.g.tr, proj(P, s));
% Ship pitches nose-up when climbing; gone once destroyed.
M = s.M;
M(:, 2) = M(:, 2) + M(:, 3) * 0.4 * tanh(s.vy / 300) + s.y;
if strcmp(s.mode, 'boom'), M = M * NaN; end
setXY(s.g.sh, proj(M, s));

% Obstacles: front and back faces of each solid slab, plus depth edges.
P = [NaN NaN NaN];
for o = s.ob
    if o.lo > 0
        P = [P; slab(-W, W, 0, o.lo, o.z)]; %#ok<AGROW>
    end
    if o.hi < H
        P = [P; slab(-W, W, o.hi, H, o.z)]; %#ok<AGROW>
    end
end
setXY(s.g.ob, proj(P, s));

% Bolts: short streaks along z.
P = [NaN NaN NaN];
for b = s.bz
    P = [P; b.x b.y b.z; b.x b.y b.z + 50; NaN NaN NaN]; %#ok<AGROW>
end
setXY(s.g.bl, proj(P, s));

% Exhaust port on the floor, then explosion rings in screen space.
z = s.L - s.d;
P = [-15 0 z - 15; 15 0 z - 15; 15 0 z + 15; -15 0 z + 15; -15 0 z - 15
    NaN NaN NaN; -15 0 z - 15; 15 0 z + 15; NaN NaN NaN; 15 0 z - 15; -15 0 z + 15];
if z > s.far, P = P * NaN; end
Q = [proj(P, s); NaN NaN];
a = linspace(0, 2 * pi, 40)';
if strcmp(s.mode, 'boom') || strcmp(s.mode, 'win')
    c = proj([0 s.y 0], s);
    if strcmp(s.mode, 'win'), c = [400 330]; end
    for r = (1:3) * 120 * min(s.t, 1.5) * (1 + strcmp(s.mode, 'win'))
        Q = [Q; c + r * [cos(a) sin(a)]; NaN NaN]; %#ok<AGROW>
    end
end
if s.spark > 0
    c = proj([0 s.h 0], s);
    r = 30 * (0.3 - s.spark) / 0.3 + 5;
    for k = 0:5
        u = [cos(k * pi / 5) sin(k * pi / 5)];
        Q = [Q; c + 0.4 * r * u; c + r * u; NaN NaN]; %#ok<AGROW>
    end
end
setXY(s.g.fx, Q);

warn = '';
if strcmp(s.mode, 'play') && s.y > s.H, warn = '   !! EXPOSED !!'; end
s.g.hud.String = sprintf('STAGE %d   SCORE %d   PORT %dm%s', ...
    s.stage, floor(s.score), max(0, round(s.L - s.d)), warn);
s.g.msg.String = s.msg;
switch s.mode
    case 'title'
        sub = 'TAP TO START';
    case 'boom'
        sub = '';
        if s.t > 1, sub = 'TAP TO RETRY'; end
    case 'win'
        sub = '';
        if s.t > 1, sub = 'TAP FOR NEXT STAGE'; end
    otherwise
        sub = '';
end
s.g.sub.String = sub;
end

function P = slab(x1, x2, y1, y2, z)
% Wireframe box spanning x1..x2, y1..y2, from depth z to z+30.
r = [x1 y1; x2 y1; x2 y2; x1 y2; x1 y1];
n = [NaN NaN NaN];
P = [r z + 0 * r(:, 1); n; r z + 30 + 0 * r(:, 1); n];
for i = 1:4
    P = [P; r(i, :) z; r(i, :) z + 30; n]; %#ok<AGROW>
end
end

function Q = proj(P, s)
% Perspective project world points (rows x,y,z) to screen; NaN behind camera.
dz = P(:, 3) + s.camZ;
dz(dz < 1) = NaN;
Q = [400 + s.f * P(:, 1) ./ dz, 330 + s.f * (P(:, 2) - s.camY) ./ dz];
end

function setXY(h, Q)
h.XData = Q(:, 1);
h.YData = Q(:, 2);
end
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Preview

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