% ptreddot
%
% Draws a red dot on gray background
%
% Thorsten Hansen 2008-05-08

myscreen = 0; % the default screen

mycolordepth = Screen(myscreen, 'PixelSizes');
if max(mycolordepth) < 16
  error('Sorry, I need a screen that supports 16- or 32-bit pixelSize.');
end

myscreensize = [0 0 512 512]; % use smaller screens for development
% myscreensize = []; % [] means "full screen"
[window, screenRect] = ...
    Screen('OpenWindow', myscreen, 0, myscreensize, max(mycolordepth));

black = BlackIndex(window);
white = WhiteIndex(window);
gray = (white + black)/2;

HideCursor;


% -------------------------------------------------------------------------
% Draw the gray background into the window
% -------------------------------------------------------------------------
Screen('FillRect', window, gray);
Screen('Flip', window);

% -------------------------------------------------------------------------
% Draw a black square
% -------------------------------------------------------------------------
sz = 100; % in pixels
color = [255 0 0]; % RGB values in [0, 255]
frameRect = [0 0 sz sz]; % rectangle the size of the square
rect = CenterRect(frameRect, screenRect); % center square on the screen
Screen('FillOval', window, color, rect);

% -------------------------------------------------------------------------
% just one flip to show the contents of the window on the screen
% -------------------------------------------------------------------------
Screen('Flip', window);
pause(4)

% done
Screen('CloseAll');
ShowCursor