clc;
clear all;
close all;
rng('shuffle');

Screen('Preference', 'SkipSyncTests', 1); 
[window, window_size] = Screen('OpenWindow', 0, [0 0 0], [],32,2);

% lets figure out the coordinates of the middle of the screen
x_mid = window_size(3)/2;
y_mid = window_size(4)/2;

% Now, lets draw some stuff
Screen('FillOval', window , [255 0 0], [x_mid-200 y_mid-200 x_mid+200 y_mid+200]);
Screen('FillRect', window , [0 255 0], [x_mid-75 y_mid-75 x_mid+75 y_mid+75]);

% and flip it to the screen
Screen('Flip',window);

% and wait for a bit
WaitSecs(3);

% and close it all down
Screen('CloseAll');