Shake on it

Jan Studnicka
/
Shake on it
on 4 Nov 2026
3
19
7
0
9987
game.m
function g = game()
%GAME Shake on It - a turn-based, one-button shop game in 1990s Prague.
%   January 1992. Communism is gone and the state auctions off its shops
%   ("small privatization"). You bought one: the business, its stock and a
%   five-year lease of the premises. Every month two or three visitors come
%   to the counter, each with one offer, and you answer with the button:
%
%       TAP        YES (once a short bar has run out)
%       TAP TAP    NO  (the second tap while the bar is still running)
%
%   At the end of each month the shop sells. Western goods bought from
%   visitors (Levi's jeans, VCRs, Jacobs coffee and Milka) sell at their
%   full retail price as far as demand goes, each good on its own shelf
%   and ledger line; the rest of the demand buys regular goods at a 20 %
%   margin. Then the bills are paid (rent, the bank loan for the auction,
%   energy) and the delayed outcomes of earlier deals arrive. Real history
%   moves the market: the Czech Republic and VAT (1993), the currency
%   split, bank failures, the end of rent controls (1995), the first
%   hypermarkets (1996) and the koruna crisis (1997). Prices follow the
%   CZSO inflation rate, and customers slowly drift away to the
%   competition. Every booking goes into the ledger down the left side,
%   newest line at the bottom.
%
%   Many offers are lies. A liar's eyes usually dart from side to side
%   (70 % of liars, 15 % of honest people); sunglasses hide them. The game
%   ends when the till is below zero at a month end. Score = months
%   survived; hold out until December 1999 to see the YEAR 2000.

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

function d = visitorTypes()
% One row per visitor type, fields separated by | (parsed by parseTable,
% so text field n is column n + 1 of s.txt):
%   numbers | honest outcome | scam outcome | outcome after refusal |
%   NAME | pitch (%d = offered amount A, / = new line, %% = %) | goods
% Numbers (money as multiples of the rolled amount A):
%   1 A (negative: fixed price -A)  2 cash on deal
%   3 goods on deal, at retail value: a seller stocks his own good, a
%     buyer (negative) takes the same share of every good on the shelf
%   4 monthly bills on deal         5 cash later (honest outcome)
%   6 months until the later outcome: honest, scam or after a refusal
%   7 scam chance                   8 cash if scam (also seizes the goods)
%   9 refusal risk                  10 cash if refused (honest only)
%   11 first month, 12 last month (0 = Jan 1992)    13 spawn weight
%   14 look, one digit each: coat colour (hue, and 1 dark to 8 light),
%      glasses (1 specs, 2 shades)
% Dad has weight 0: he only appears as the very first visitor.
% Background: Levi's from Munich and VCRs from Vienna's Mexikoplatz dodged
% customs and the 1992 import surcharge (10-15 %); by September 1991 firms
% owed each other Kčs 147 bn in unpaid invoices; racketeers sold
% "protection"; a coupon book cost Kčs 1035 and the Harvard funds promised
% to buy it back for ten times that; rent controls on shops ended on
% 1 October 1995; new banks lured deposits with high interest and many
% failed (deposits insured at 80 % from 1994).
d = {
    '10000 1 0 0 0 0 0 0 0 0 99 99 0 41||||DAD|Proud of you, son. Take %d.|'
    '30000 -1 2.5 0 0 0 .3 -.2 0 0 0 99 4 30||Fake jeans! Inspectors took them.||IMPORTER|Fifty Levi''s 501 from Munich./%d the lot.|Jeans'
    '40000 -1 2.2 0 0 0 .25 -.3 0 0 1 99 2 32||Customs seized the VCRs. Fined!||DEALER|Six VCRs from Vienna, no duty paid./%d cash.|VCRs'
    '20000 -1 1.8 0 0 0 .1 0 0 0 0 99 3 50||Stale coffee. Binned.||WHOLESALER|Jacobs coffee and Milka from Vienna./%d a pallet.|Coffee, Milka'
    '30000 0 -1 0 1.2 2 .35 0 0 0 2 99 1.5 61|The Brno trader paid.|The Brno trader never paid.||TRADER|I''ll take %d of goods to Brno./+20 %%, invoice due in two months.|'
    '30000 1 0 0 -1.2 1 0 0 0 0 1 99 1 22|Mr. Black came to collect.|||LOAN SHARK|Short on cash? %d now,/a fifth more back next month.|'
    '3000 -1 0 0 0 0 0 0 .6 -2 2 71 1.3 12|||They smashed your window.|RACKETEER|Nice shop. Shame if it burned./%d keeps you safe.|'
    '3000 0 0 1 0 12 0 0 .5 -10 45 56 1 70|||Lease not renewed. Moving cost.|LANDLORD|Rent caps are gone: +%d a month,/or no new lease for you.|'
    '-1035 -1 0 0 9.662 12 .3 0 0 0 1 1 4 21|The fund paid 10000!|The fund was tunnelled.||FUND MANAGER|Sign your %d coupon book to my fund./I''ll buy it back for 10000 in a year!|'
    '30000 -1 0 0 1.15 12 .3 .8 0 0 24 59 1 81|The bank paid 15 %.|Bank bust! Insurance paid 80 %.||BANKER|Deposit %d with our new bank./15 %% interest a year!|'
    };
end

function n = newsItems()
% Historical news, one row each: month (0 = Jan 1992), demand factor,
% bills factor | ledger text. Booked at the end of its month.
n = {
    '12 .9 1.15|Czech Republic born. VAT, insurance.'
    '13 1 1|Kčs becomes Kč. Old notes get stamps.'
    '26 1 1|Banka Bohemia collapses.'
    '45 1 1.2|Rent controls end.'
    '57 .9 1|Tesco buys Kmart.'
    '58 .92 1|First hypermarket opens in Brno.'
    '60 1 1.4|Your five-year lease ends.'
    '64 .9 1|Koruna crisis. Customers save.'
    };
end

function s = initState(ax)
ax.Color = [.6 .7 .6];                          % the shop's wall

% Parse both tables. spec is numeric; txt columns: numbers, honest, scam,
% refused, name, pitch, goods; nt columns: numbers, news.
[s.spec, s.txt] = parseTable(visitorTypes());
[s.nw, s.nt] = parseTable(newsItems());

% The scene as layers, back to front, one row per object:
% "name type colour numbers". Colour: three digits, red green blue in
% ninths. Types:
%   g  layer (hgtransform); the rows below it belong to it
%   r  rectangles "x0 y0 x1 y1 ...", several make one patch
%   p  polygon "x1 y1 x2 y2 ..."
%   t  text "x y size", anchored at its bottom left, TeX markup
% Patches get an outline in half their colour. Rows named z are
% anonymous; the rest become handles in s.g. The ledger fills the left
% strip x < 270, newest line at the bottom; the shop is right of it.
G = {
    'z g 0'                                     % the shop
    'z r 421 462 250 608 466'                   % door frame
    'z r 997 470 250 600 458'                   % open door, sunny street
    'z r 443 270 0 800 250'                     % floor
    'z r 999 300 365 410 440'                   % wall calendar
    'z r 822 300 420 410 440'
    'day t 111 306 380 20'
    'z r 642 615 255 785 263 615 320 785 328 615 385 785 393'   % shelves
    'jn t 238 618 258 26'                       % jeans, VCRs, coffee & Milka
    'vc t 111 618 323 26'
    'cf t 521 618 376 26'
    'man g 0'                                   % the visitor, feet at y=0
    'z r 111 -40 0 -3 205 3 0 40 205'           % legs
    'coat p 333 -70 200 70 200 76 375 60 408 22 418 -22 418 -60 408 -76 375'
    'z p 865 -50 478 -46 446 -30 422 0 414 30 422 46 446 50 478 0 500'  % face
    'z p 211 -50 478 -40 512 0 526 40 512 50 478 0 500'     % hair
    'eyes r 000 -25 471 -13 479 13 471 25 479'
    'gl p 000 -34 466 -4 466 -4 480 4 480 4 466 34 466 34 486 -34 486'  % glasses: lenses cover the eyes +-7 with margin
    'z r 511 -14 436 14 442'                    % mouth
    'z g 0'                                     % counter and till
    'z r 531 270 0 800 185'
    'z r 421 290 20 520 150 550 20 780 150'     % counter panels
    'z r 333 280 150 460 250'                   % cash register
    'cash t 393 290 160 18'
    'z r 998 0 0 270 600'                       % ledger
    'log t 111 6 6 9'
    'arm g 0'                                   % your own arm
    'z p 678 650 -20 760 -20 770 85 690 95'
    'z p 865 692 100 705 78 765 78 778 100 765 122 705 122'
    'bub g 0'                                   % speech bubble
    'z p 999 285 470 510 470 530 432 550 470 785 470 785 580 285 580'
    'bar r 000 300 480 600 488'                 % double-tap window
    'say t 000 300 494 14'
    'ov g 0'                                    % title / game-over overlay
    'ovb r 000 270 0 800 600'
    'ovT t 998 290 150 12'
    };
for q = G'
    w = split(q{1});
    k = w{2};
    m = (w{3} - 48)/9;
    v = str2double(w(4:end))';
    x = v(1:2:end);
    y = v(2:2:end);
    if k == 'r'
        x = x([1; 2; 2; 1] + (0:2:end - 1));
        y = y([1; 1; 2; 2] + (0:2:end - 1));
    end
    if k == 'g'
        P = hgtransform(ax);
        o = P;
    elseif k == 't'
        o = text(P, x(1), y(1), '', 'Color', m, 'FontSize', x(2), 'FontName', 'Courier New', 'VerticalAlignment', 'bottom');
    else
        o = patch(P, x, y, m, 'EdgeColor', m/2);
    end
    s.g.(w{1}) = o;
end
s.g.ovb.FaceAlpha = .85;
set(findall(ax.Children), 'HitTest', 'off', 'PickableParts', 'none');
s.eyeX = s.g.eyes.XData;
s = resetRound(s);
[s.best, s.clock, s.mode, s.modeT] = deal(0);   % title screen
s.ov = {'\fontsize{34}\bfSHAKE ON IT\rm\fontsize{12}','', 'Prague, January 1992. Communism is gone.', 'At a state auction you bought a little shop:', 'its stock, its counter and a five-year lease.', 'Every month: takings in, rent and bank out.', 'Survive the nineties.', '', 'TAP = YES   TAP TAP = NO', '', 'TAP TO OPEN THE SHOP'};
end

function [n, t] = parseTable(rows)
% Split "numbers|text|text..." rows into a numeric matrix n and a cell
% array t of all fields; t(:, 1) still holds the numbers as text.
t = split(rows, '|');
n = str2double(split(t(:, 1)));
end

function s = resetRound(s)
% Fresh business, January 1992, already open (mode 1). Amounts in Kčs:
% cash, Western goods on the shelves (retail value, one row per visitor
% type that sells them), monthly demand and bills, price index, 50 empty
% ledger lines. Graphics and the best score survive.
v = {'mode', 1, 'cash', 40000, 'stock', 0*s.spec(:, 1), 'dem', 90000, 'burn', 20000, 'ix', 1, 't', 0, 'left', 2, 'E', zeros(0, 5), 'log', repmat({''}, 1, 50), 'ph', 0, 'pt', 0, 'vt', 0, 'tap', 0, 'lines', {''}, 'shk', -9};
for k = 1:2:numel(v)
    s.(v{k}) = v{k + 1};
end
end

function s = updateState(s, dt, pressed)
s.clock = s.clock + dt;
if s.mode ~= 1
    if pressed && s.clock - s.modeT > 1
        s = resetRound(s);
    end
    return
end

% Visitor cycle: 0 empty shop, 1 walking in, 2 offer, 3 reply and leave.
% An offer waits as long as it takes. Its first tap opens a 0.9 s
% window: a second tap inside it means NO, letting it run out means YES.
% Taps outside offers are ignored. The month closes after its last
% visitor has left.
s.pt = s.pt + dt;
D = [.4 1 9 1.4];
if s.ph == 2
    if pressed && ~s.tap
        s.tap = s.clock;
    elseif pressed || s.tap && s.clock - s.tap > .9
        s = closeDeal(s, ~pressed);
    end
elseif s.pt > D(s.ph + 1)
    s.pt = 0;
    s.ph = mod(s.ph + 1, 4);
    if s.ph == 1
        s = newVisitor(s);
    elseif ~s.ph && s.left < 1
        s = closeMonth(s);
    end
end
end

function s = closeMonth(s)
% Delayed outcomes that are due, one column e per outcome: [due month;
% cash; change of the visitor's goods; visitor type; txt column].
due = s.E(:, 1) <= s.t;
for e = s.E(due, :)'
    s = addCash(s, e(2), s.txt{e(4), e(5)});
    s.stock(e(4)) = max(s.stock(e(4)) + e(3), 0);
end
s.E(due, :) = [];

% The month's news, inflation (CZSO, % a year) and competition, which
% takes 0.5 % of the customers every month.
k = s.nw(:, 1) == s.t;
s = addCash(s, 0, [s.nt{k, 2}]);
r = [11.1 20.8 10 9.1 8.8 8.5 10.7 2.1];
f = (1 + r(floor(s.t/12) + 1)/100)^(1/12);
s.ix = f*s.ix;
s.burn = f*prod(s.nw(k, 3))*s.burn;
s.dem = .995*f*prod(s.nw(k, 2))*s.dem;

% Takings, one ledger line each (zero lines are skipped): Western goods
% sell first at full price, every good the same share of its stock, the
% rest of the demand buys everyday goods at a 20 % margin; then the bills.
% Seasons (x10): quiet Jan-Feb, tourists in summer, Christmas in December.
m = '889::;<<:::>' - 48;
d = s.dem*m(mod(s.t, 12) + 1)*(.08 + .04*rand);
v = s.stock*min(1, d/sum(s.stock));
s.stock = s.stock - v;
w = round([v; .2*(d - sum(v)); -s.burn]);
n = [strcat(s.txt(:, 7), ' sold'); {'Everyday goods, 20 % margin'; 'Rent, bank loan, energy'}];
for k = find(w)'
    s = addCash(s, w(k), n{k});
end
if s.cash < 0 || s.t > 94
    n = s.t + 1;
    r = {'The street ate you alive.', 'A respected merchant.', 'A tycoon of the nineties!'};
    T = {'BANKRUPT', 'YEAR 2000'};
    s.best = max(s.best, n);
    s.mode = 2;
    s.modeT = s.clock;
    s.ov = {['\fontsize{34}\bf' T{1 + (s.cash >= 0)} '\rm\fontsize{12}'], '', sprintf('Months survived: %d (best %d).', n, s.best), r{sum(n >= [0 18 48])}, '', 'TAP TO TRY AGAIN'};
end

% Next month: 2-3 visitors after a pause to read the ledger.
s.t = s.t + 1;
s.left = 1 + randi(2);
s.pt = -1.2;
end

function s = newVisitor(s)
% Dad always opens the story; later visitors are drawn by weight from the
% types active this month, never the same type twice in a row. Offers
% grow with inflation; a negative A is a fixed price.
k = 1;
if s.vt
    w = s.spec(:, 13).*(s.spec(:, 11) <= s.t & s.t <= s.spec(:, 12));
    w(s.vt) = 0;
    k = find(cumsum(w) >= rand*sum(w), 1);
end
c = s.spec(k, :);
s.vt = k;
s.tap = 0;
s.left = s.left - 1;
s.scam = rand < c(7);
s.shifty = rand < .15 + .55*s.scam;
s.amt = max(-c(1), round(c(1)*s.ix*(.7 + .6*rand)/100)*100);
s.lines = [{['\bf' s.txt{k, 5} '\rm']}; split(sprintf(s.txt{k, 6}, s.amt), '/'); {'\fontsize{9}TAP = YES   TAP TAP = NO'}];
end

function s = closeDeal(s, yes)
% Apply a handshake (yes) or a refusal and queue what happens later. A
% deal needs the cash or the goods up front. Every later outcome comes
% c(6) months after this one, at that month's end.
k = s.vt;
c = s.spec(k, :);
a = s.amt;
q = ~s.scam;
g = sum(s.stock);
ok = yes && all([s.cash g] + c(2:3)*a >= 0);
if ok
    s = addCash(s, c(2)*a, s.txt{k, 5});
    s.stock = s.stock*min(1, 1 + c(3)*a/g);     % a buyer takes a share of every good
    s.stock(k) = s.stock(k) + max(c(3), 0)*a;   % a seller's goods go on the shelf
    s.burn = s.burn + c(4)*a;
    s.shk = s.clock;
    s.E(end + 1, :) = [s.t + c(6), c(8 - 3*q)*a, -max(c(3), 0)*a*~q, k, 3 - q];
elseif q && rand < c(9)
    s.E(end + 1, :) = [s.t + c(6), c(10)*a, 0, k, 4];
end
r = {'Deal!', 'Your loss.', 'Can''t cover it. No deal.'};
s.lines = [s.lines(1) r(1 + ~yes + 2*(yes > ok))];
s.ph = 3;
s.pt = 0;
end

function s = addCash(s, v, m)
% Book a change of cash (v) with a dated ledger line "MM/YY m +v". An
% empty m with no cash books nothing ('' is the only text an if treats as
% false).
s.cash = s.cash + v;
if v
    m = sprintf('%s %+d', m, round(v));
end
if m
    s.log = [s.log(2:end) {sprintf('%02d/%d %s', mod(s.t, 12) + 1, 92 + floor(s.t/12), m)}];
end
end

function renderFrame(~, s)
% Pure function of the state: all animation is derived from clocks here.
h = s.g;
ph = s.ph*(s.mode == 1);

% The visitor: walk progress p (0 at the door, 1 at the counter, eased,
% bobbing with the steps), dressed by the look digits (coat 1 dark to 8
% light, glasses 1 specs / 2 shades).
p = [0, s.pt, 1, 1 - (s.pt - .6)/.8];
p = min(max(p(ph + 1), 0), 1);
p = p*p*(3 - 2*p);
if ph > 0
    c = num2str(s.spec(s.vt, 14)) - 48;
    h.coat.FaceColor = hsv2rgb([c(1)/10 .4 .2 + c(1)/12]);
    set(h.gl, 'Visible', c(2) > 0, 'FaceAlpha', +(c(2) > 1));
    h.man.Matrix = makehgtform('translate', [535 255 - 365*p + 9*abs(sin(9*s.clock))*(p < 1) 0], 'scale', .33 + .67*p);
    h.eyes.XData = s.eyeX + (ph == 2)*s.shifty*7*sign(sin(s.clock*4.5));
end

% Your arm shakes hands.
a = s.clock - s.shk;
h.arm.Matrix = makehgtform('translate', [-170 150 0]*(a < .8)*sin(pi*a/.8));

% Speech bubble with the double-tap bar, overlay, every good on its own
% shelf (stock rows 2-4 are the sellers of jeans, VCRs and coffee; a
% piece per 10000, at most 10), calendar, till with the cash (Kčs until
% January 1993, then Kč) and the monthly bills, and the ledger.
set([h.man h.bub h.bar h.ov], {'Visible'}, {ph > 0; ph > 1; ph == 2 && s.tap > 0; s.mode ~= 1});
h.bar.XData = 300 + [0 1 1 0]*300*(1 - (s.clock - s.tap)/.9);
n = min(ceil(s.stock/1e4), 10);
set([h.jn h.vc h.cf h.say h.day h.cash h.log h.ovT], {'String'}, {repelem('▌', n(2)); repelem('◘', n(3)); repelem('▪', n(4)); s.lines; upper(string(datetime(1992, s.t + 1, 1), 'MMM yyyy', 'en_US')); sprintf('\\bf%d %.*s\n\\rm\\fontsize{9}bills %d', round(s.cash), 3 - (s.t > 12), 'Kčs', round(s.burn)); s.log; s.ov});
end
Play Game
Preview

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