Blocks in scratch are organized into categories listed in the top left panel. The simplest categories are the four on the left Motion, Looks, Sound, and Pen. The four categories on the right will be dealt with in Chapter 2.
If you click on the Motion tab, you will see a list of statements that control the location and rotation of sprites. The most basic movements are steps and roatations. You can experiment with how these commands change the Sprite by double clicking them.
A sprite's position on the stage is determined by X and Y coordinates. The X coordinate determines the horizontal (i.e. right to left) position of the sprite. The Y coordinate determines the vertical (i.e. top to bottom) position of the sprite. Because any location on the stage can be specified with 2 numbers we say that the Stage is a 2-dimensional plane. Stage coordinates can be determined by moving the mouse around over the stage. The origin (i.e. the coordinates X = 0 and Y = 0) is at the center of the stage. A sprite can be moved to an exact position on the stage by using the following statements. Try each of them out:
A sprite's rotation is measured in degrees where 360 degrees is a full circle. 0 degrees is rotated to the X-Axis. Thus, turning by 90 degrees is a quarter turn of a circle. A sprite can be rotated to an exact degree by using the following. When other sprites are on the screen, the "Point to" statement can be used to point one sprite towards the direction of another.
Note that all of these blocks have two notches except for the three blocks (x position, y position, direction) at the bottom of the Motion panel which have rounded edges. This is because these are properties rather than commands. Double-clicking properties will display their value but will have no effect on anything on the Stage.
If you click the check boxes beside the properties you can get their values to display directly on the stage.
