% Clear the workspace and the screen
close all;
clear;
sca

% Randomly seed the random number generation
rng('shuffle');

% Here we call some default settings for setting up Psychtoolbox
PsychDefaultSetup(2);

% Get the screen numbers
screens = Screen('Screens');

% Select the external screen if it is present, else revert to the native
% screen
screenNumber = max(screens);

% Define black
black = BlackIndex(screenNumber);

% Open an on screen window and color it grey
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, black);

% Get the vertical refresh rate of the monitor
ifi = Screen('GetFlipInterval', window);

% Set the blend funciton for the screen
Screen('BlendFunction', window, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');

% Get the size of the on screen window in pixels
% For help see: Screen WindowSize?
[screenXpixels, screenYpixels] = Screen('WindowSize', window);

% Get the centre coordinate of the window in pixels
% For help see: help RectCenter
[xCenter, yCenter] = RectCenter(windowRect);

% We set the text size to be nice and big here
Screen('TextSize', window, 300);

% We will be presenting each of our numbers 10 through 0 for one seconds
% each
presSecs = 1;
waitframes = round(presSecs / ifi);

% We change the color of the number every "nominalFrameRate" frames
colorChangeCounter = 0;

% Randomise a start color
color = rand(1, 3);

% Starting number
currentNumber = 10;

% Maximum priority level
topPriorityLevel = MaxPriority(window);
Priority(topPriorityLevel);

% Flip to the vertical retrace rate
vbl = Screen('Flip', window);

% We use a while loop to count down. On each iteration of the loop we use a
% waitframes value greater than 1 so that each number is presented for one
% second
while currentNumber >= 0

    % Convert our current number to display into a string
    numberString = num2str(currentNumber);

    % Draw our number to the screen
    DrawFormattedText(window, numberString, 'center', 'center', color);

    % Flip to the screen
    vbl = Screen('Flip', window, vbl + (waitframes - 0.5) * ifi);

    % New random colour for the next number
    color = rand(1, 3);

    % Increment the number
    currentNumber = currentNumber - 1;

end

% Wait a second before closing the screen
WaitSecs(1);

% Clear the screen
close all;
sca

Published with MATLAB® R2022a