This document clarifies the dimension specification for flipper and specifies the convention for flipper rotation and placement in the standard file format. This clarification replaces all of the Flipper description in Appendix 1, Section 14 of the original final project handout.

Flipper Dimension

The Project document specifies that: "Each flipper has an edge length 2L (takes up a 2x2L space)."  The edge length refers to the size of the square bounding box.  During run mode, a flipper must not extend outside its 2L by 2L bounding box at any point in its motion.

Flipper Orientation and Rotation in the Standard File Format

The diagrams below show the initial orientations for Left Flippers and Right Flippers in the standard file format. A standard file format Rotate command, when applied to a flipper, performs a 90 degree clockwise rotation of the flipper's entire bounding box. That is, the pivot of the flipper moves to an adjacent part of the bounding box, but the bounding box itself does not change. The direction of motion (clockwise or counterclockwise) of a flipper does not change due to a Rotate command.

You are only required to support positioning or rotating flippers at 90 degree angles. Placement at 45 degree angles is not required.

Left Flipper

Left flippers initially rotate counterclockwise in run mode. The pivot of a left flipper is initially in the top left corner of the bounding box. The other end is in the bottom left corner.

After one Rotate command, the pivot of the left flipper is in the top right corner of the bounding box. The other end is in top right corner. The direction of motion is still counterclockwise.

Right Flipper

Right flippers initially rotate clockwise in run mode. The pivot of a right flipper is initially in the top left corner of the bounding box. The other end is in the top right corner.

After one Rotate command, the pivot of the right flipper is in the top right corner and the other end is in the bottom right corner. The direction of motion is still clockwise.

Notes

Note that the term "rotate" has one meaning for run mode, and another for build mode and the standard file format.

Again, the shape and design of the flippers here (as in Appendix 1) are for illustrative purposes only.  Your final design may differ.

Other Considerations

The following parts of the original flipper specification are unchanged:

• In build mode, your program should reject attempts by the user to place a flipper (or rotate it) in such a way that it will extend outside its 2L by 2L bounding box at any point in its motion.
• When its action is triggered by something connected to it, a standard flipper behaves as follows. It rotates around its center of rotation at a constant angular velocity of 30 degrees per time unit, to a position 90 degrees away from its starting position. When its action is triggered a second time, it rotates back to its original position at an angular velocity of 30 degrees per time unit. If its action is triggered while the flipper is rotating, it should wait until it finishes rotating before responding to the action. During run mode rotation, the flipper should always remain entirely within its bounding box.
• As with the three standard bumpers, a flipper generates a trigger whenever the ball hits it.
• The standard coefficient of reflection for a flipper is 0.95. However, when computing the behavior of a ball bouncing off the flipper, you must include the linear velocity of the part of the flipper that contacts the ball; therefore the ball may leave the flipper with a higher energy than it had when it reached it.