1. Make a sketch program. When the left mouse button is pressed and dragged, the track will be drawn along with the mouse position in the window. When the left mouse button is raised, it will not be drawn.
2. Make an input program in the graphics window. When the user presses the key, the character represented by the pressed key will appear in the graphics window, and automatically advance to the right like the input box of the graphical interface. Press enter to finish the input, and the user's input content will be displayed in the terminal window. On this basis, the current position of the cursor flicker, and support left and right direction keys and two delete keys.