Reversi

on 10 Nov 2026
1
25
5
3
6816
game.m
function g = game()
g.init   = @initState;
g.update = @updateState;
g.render = @renderFrame;
end

function state = initState(ax)
state = struct();
state.turn = 1;       % 1 = black(player), -1 = white(AI)
state.winner = 0;     % 0 = playing, 1/2/3 = win/lose/draw
state.K = [4 4; 5 5]; % Black pieces
state.W = [4 5; 5 4]; % White pieces
state.s2i = @(X) sub2ind([8, 8], X(:, 1), X(:, 2));
state.bd = zeros(8, 8);
state.bd(state.s2i(state.K)) = 1;
state.bd(state.s2i(state.W)) = -1;
state.cl = [.64 .55 .33; .38 .16 .01; .14 .29 .16; .22 .49 .27];
state.pressA = 0;
state.pressT = 0;
state.idx = 1;
state.P = nan(0, 2);
state.A = getA(state.bd, state.turn);

fill(ax, [-3;3;3;-3]*[100, 98, 80] + 400, [-3;-3;3;3]*[100, 98, 80] + 300, ...
    [1;2;4], 'EdgeColor','none'); colormap(ax, state.cl)
tx = (-2.625:.75:3)*80; ty = ones(1,8)*265; state.i2p = tx(:);
text(ax, [tx, -ty] + 400, [ty, -tx] + 300, [char((65:72).'); num2str((1:8).')], ...
    'FontSize',21, 'FontWeight','bold', 'Color',state.cl(1,:), 'HorizontalAlignment','center')
gx = linspace(-3,3,9)*80; gy = ones(1, 9)*240;
plot(ax, [gx, gy; gx, -gy] + 400, [gy, gx; -gy, gx] + 300, 'Color',state.cl(3,:), 'LineWidth',2)
scatter(ax, [-3;3;3;-3]*40 + 400, [-3;-3;3;3]*40 + 300, 100, state.cl(3,:), 'filled')

state.wHdl = scatter(ax, nan, nan, 800, 'w', 'filled');
state.kHdl = scatter(ax, nan, nan, 800, 'k', 'filled');
state.pHdl = scatter(ax, nan, nan, 300, 'g', 'LineWidth',2);
state.aHdl = scatter(ax, nan, nan, 300, 'g', 'LineWidth',2, 'Marker','x');
state.ogoT = 0;

text(ax, 50, 20, {'Pressing the spacebar initiates move-position selection,' ;'and pressing the spacebar again places the piece.'}, 'FontSize',17, 'Rotation',90);
state.winHdl = text(ax, 750, 550, ' ', 'FontSize',21, 'FontWeight','bold', 'HorizontalAlignment','center');
end

function state = updateState(state, dt, pressed)
state.winner = judge(state.bd);
if state.winner == 0
    if state.turn == 1
        if pressed 
            if state.pressT == 1 && state.pressA > 0
                state.pressA = 0;
                state.turn = -1;
                state.ogoT = 0;
            end
            state.pressT = mod(state.pressT + 1, 2);
        end
        if state.pressT == 1
            state.pressA = state.pressA + 1;
            state.idx = floor(state.pressA/20);
            state.P = state.A(mod(state.idx, size(state.A, 1)) + 1, :);
        end
    else
        if state.ogoT == 0
            state.ogoT = 1;
            state.bd = changeC(state.bd, state.P, 1);
            state.K = findV(state.bd, 1);
            state.W = findV(state.bd, -1);
            % state.winner = judge(state.bd);
            % state.ogoT = 2;
        end
        if state.ogoT >= 1
            if state.ogoT < 2
                state.ogoT = state.ogoT + .05;
            else
                state.ogoT = 2;
            end
        end
        if state.ogoT == 2
            state.ogoT = 3;
            state.A = getA(state.bd, -1);
            if isempty(state.A)
                state.A = getA(state.bd, 1);
                state.turn = 1;
                state.P = nan(0, 2);
            else
                state.P = algGetP(state.A, state.bd);
                state.bd = changeC(state.bd, state.P, -1);
                state.K = findV(state.bd, 1);
                state.W = findV(state.bd, -1);
                % state.winner = judge(state.bd);
            end
            state.ogoT = 4;
        end
        if state.ogoT == 4
            state.ogoT = 5;
            state.A = getA(state.bd, 1);
            if isempty(state.A)
                state.ogoT = 1;
            else
                state.turn = 1;
            end
        end
    end
else
    winStr = {'You Win!', 'You lose!', 'Draw'};
    state.winHdl.String = winStr{state.winner};
end

end

function renderFrame(~, state)
state.wHdl.XData = state.i2p(state.W(:,1)) + 400;
state.wHdl.YData = state.i2p(state.W(:,2)) + 300;
state.kHdl.XData = state.i2p(state.K(:,1)) + 400;
state.kHdl.YData = state.i2p(state.K(:,2)) + 300;
state.aHdl.XData = state.i2p(state.A(:,1)) + 400;
state.aHdl.YData = state.i2p(state.A(:,2)) + 300;
state.pHdl.XData = state.i2p(state.P(:,1)) + 400;
state.pHdl.YData = state.i2p(state.P(:,2)) + 300;
end


function A = getA(B, t)
% Find all legal moves for player t
[X, Y] = find(B == t); P = [X, Y]; 
d = [1 0; -1 0; 0 1; 0 -1; 1 1; -1 -1; 1 -1; -1 1];
if ~isempty(P)
    D = repmat(kron(P, ones(8, 1)), 1, 7) + kron(1:7, repmat(d, size(P, 1), 1));
    D(any(D(:, 1:2) > 8, 2) | any(D(:, 1:2) < 1, 2), :) = [];
    D(B(D(:, 1) + (D(:, 2) - 1).*8) ~= -t, :) = [];
    DX = D(:, 1:2:end); DY = D(:, 2:2:end);
    bool = DX < 1 | DX > 8 | DY < 1 | DY > 8;
    DX(bool) = P(1, 1); DY(bool) = P(1, 2);
    [~, col] = max(B(DX + (DY - 1).*8) ~= -t, [], 2);
    idx = sub2ind(size(DX), (1:size(DX, 1)).', col);
    idx = idx(B(DX(idx) + (DY(idx) - 1).*8) == 0);
    A = [DX(idx), DY(idx)];
    A = sortrows(A);
else
    A = nan(0, 2);
end
end

function B = changeC(B, P, t)
% Place piece at P for player t and flip captured pieces
d = [1 0; -1 0; 0 1; 0 -1; 1 1; -1 -1; 1 -1; -1 1];
D = repmat(kron(P, ones(8, 1)), 1, 7) + kron(1:7, d);
DX = D(:, 1:2:end); DY = D(:, 2:2:end);
bool = DX < 1 | DX > 8 | DY < 1 | DY > 8;
DX(bool) = P(1, 1); DY(bool) = P(1, 2); 
T = B(DX + (DY - 1).*8)*t;
bool = T(:, 1) == -1;
DX = DX(bool, :); DY = DY(bool,:); T = T(bool, :);
[V, Ti] = max(diff(T, 1, 2) == 2, [], 2);
DX = DX(V, :); DY = DY(V, :); Ti = Ti(V);
for i = 1:length(Ti)
    B(DX(i, 1:Ti(i)) + (DY(i, 1:Ti(i)) - 1).*8) = t;
end
B(P(1), P(2)) = t;
end

function xy = findV(B, v)
[x, y] = find(B == v);
xy = [x, y];
end

function P = algGetP(A, B)
% AI move selection: prefer corner, else random
C = find((A(:,1) == 1 | A(:,1) == 8) & (A(:,2) == 1 | A(:,2) == 8));
if ~isempty(C)
    P = A(C(1), :);
else
    P = A(randi(size(A, 1), 1), :);
end
end

function w = judge(B)
% Determine winner: 0=playing, 1=win, 2=lose, 3=draw
f = isempty([getA(B, 1); getA(B, -1)]);
w = 0;
bl = length(find(B == 1));
wl = length(find(B == -1));
switch 1
    case ((all(all(B)) || f) && bl > wl) || wl == 0, w = 1;
    case ((all(all(B)) || f) && bl < wl) || bl == 0, w = 2;
    case  (all(all(B)) || f) && bl == wl, w = 3;
end
end
Play Game
Preview

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