% Set the color of our dot to full red.
dotColor = [1 0 0];

% Determine a random X and Y position for our dot. 
dotXpos = rand * screenXpixels;
dotYpos = rand * screenYpixels;

% Dot size in pixels
dotSizePix = 20;

% Draw the dot to the screen.
Screen(\'DrawDots\', window, [dotXpos dotYpos], dotSizePix, dotColor, [], 2);

% Flip to the screen. 
Screen(\'Flip\', window);

% Use the meshgrid command to create our base dot coordinates. This will      使用网格命令创建点坐标
% simply be a grid of equally spaced coordinates in the X and Y dimensions,
% centered on 0,0
dim = 10;
[x, y] = meshgrid(-dim:1:dim, -dim:1:dim);

% Here we scale the grid so that it is in pixel coordinates. We just scale            对网格进行调整，使其处于像素坐标内，并适合于屏幕尺寸
% it by the screen size so that it will fit. This is simply a
% multiplication. Notive the "." before the multiplicaiton sign. This
% allows us to multiply each number in the matrix by the scaling value.
pixelScale = screenYpixels / (dim * 2 + 2);
x = x .* pixelScale;
y = y .* pixelScale;

% Calculate the number of dots       计算点的数量
numDots = numel(x);

% Make the matrix of positions for the dots. This need to be a two row               制作点的坐标矩阵。是一个2*n的形式，第一行为x坐标，第二行为y坐标
% vector. The top row will be the X coordinate of the dot and the bottom           每一列代表一个点
% row the Y coordinate of the dot. Each column represents a single dot. 
dotPositionMatrix = [reshape(x, 1, numDots); reshape(y, 1, numDots)];

% We can define a center for the dot coordinates to be relaitive to. Here            定义点的中心
% we set the centre to be the centre of the screen
dotCenter = [xCenter yCenter];

% Set the color of our dot to be random            设置颜色
dotColors = rand(3, numDots) .* white;

% Set the size of the dots randomly between 10 and 30 pixels      设置点的大小在10-30之间
dotSizes = rand(1, numDots) .* 20 + 10;

% Draw all of our dots to the screen in a single line of code         绘制点
Screen(\'DrawDots\', window, dotPositionMatrix,...
    dotSizes, dotColors, dotCenter, 2);

% Flip to the screen.
Screen(\'Flip\', window);

% Make a base Rect of 200 by 200 pixels.     制作一个200*200像素的矩形
baseRect = [0 0 200 200];

% Center the rectangle on the centre of the screen using fractional pixel values.  将此矩形调整到以某个点为中心，返回值为新矩形的坐标
centeredRect = CenterRectOnPointd(baseRect, xCenter, yCenter);

% Set the color of our square to full red.
rectColor = [1 0 0];

% Draw the square to the screen.
Screen(\'FillRect\', window, rectColor, centeredRect);

% Flip to the screen.
Screen(\'Flip\', window);

% Make a base Rect of 200 by 200 pixels   基准矩形
baseRect = [0 0 200 200];

% Screen X positions of our three rectangles   这三个矩形的x坐标
squareXpos = [screenXpixels * 0.25 screenXpixels * 0.5 screenXpixels * 0.75];
numSqaures = length(squareXpos);

% Set the colors to Red, Green and Blue  颜色依次为红绿蓝
allColors = [1 0 0; 0 1 0; 0 0 1];

% Make our rectangle coordinates   制作坐标
allRects = nan(4, 3);
for i = 1:numSqaures
    allRects(:, i) = CenterRectOnPointd(baseRect, squareXpos(i), yCenter);
end

% Draw the rect to the screen
Screen(\'FillRect\', window, allColors, allRects);

% Flip to the screen
Screen(\'Flip\', window);

% Make a base Rect of 200 by 200 pixels
baseRect = [0 0 200 200];

% Screen X positions of our three rectangles
squareXpos = [screenXpixels * 0.25...
    screenXpixels * 0.5 screenXpixels * 0.75];
numSqaures = length(squareXpos);

% Set the colors to Red, Green and Blue
allColors = [1 0 0; 0 1 0; 0 0 1];

% Make a multiplier to modulate the size of our squares
sizeChanger = [0.7 1 1.3];

% Make our rectangle coordinates
allRects = nan(4, 3);
for i = 1:numSqaures
    allRects(:, i) = CenterRectOnPointd(baseRect .* sizeChanger(i),...
        squareXpos(i), yCenter);
end

% Draw the rect to the screen
Screen(\'FillRect\', window, allColors, allRects);

% Flip to the screen
Screen(\'Flip\', window);

% Make a base Rect of 200 by 200 pixels
baseRect = [0 0 200 200];

% Screen X positions of our three rectangles
squareXpos = [screenXpixels * 0.25 screenXpixels * 0.5 screenXpixels * 0.75];
numSquares = length(squareXpos);

% Set the colors to Red, Green and Blue
allColors = [1 0 0; 0 1 0; 0 0 1];

% Make our rectangle coordinates
allRects = nan(4, 3);
for i = 1:numSquares
    allRects(:, i) = CenterRectOnPointd(baseRect, squareXpos(i), yCenter);
end

% Pen width for the frames
penWidthPixels = 6;

% Draw the rect to the screen
Screen(\'FrameRect\', window, allColors, allRects, penWidthPixels);

% Flip to the screen
Screen(\'Flip\', window);

% Make a base Rect of 200 by 250 pixels
baseRect = [0 0 200 250];

% For Ovals we set a miximum diameter up to which it is perfect for
maxDiameter = max(baseRect) * 1.01;

% Center the rectangle on the centre of the screen
centeredRect = CenterRectOnPointd(baseRect, xCenter, yCenter);

% Set the color of the rect to red
rectColor = [1 0 0];

% Draw the rect to the screen
Screen(\'FillOval\', window, rectColor, centeredRect, maxDiameter);

% Flip to the screen
Screen(\'Flip\', window);