nsb13, touch overlapping objects

[heppg]

Scenario: have two sprites, partially overlapping. A third sprite 'grey' is moving with the mouse, and when touching red or blue sprite it triggers some action. (The sample is simplified from a RGB driving example, where scratch controls the color of a RGB attached. I have seen the RGB flickerung unexpectedly.)

See code in http://heppg.de/ikg/wordpress/wp-content/uploads/2014/11/touch_red_blue.zip

Expected:

• when green touched, text 'green' is displayed
• when red touched, text 'red' is displayed
• on overlapping region, the top sprite 'wins' and 'red' is displayed

Current:

• on overlapping area, text 'red' and 'green' are displayed alternating.

Problem

• topmost sprite should preventing underlying sprites to be touched. Unexpected behaviour.

In legacy scratch, unfortunately this is the same behavior.