Can't use buttons behind reference line

[elisemorgan]

Test device: iPad 2, Lave

Operating System: iOS 8.4.1

Browser: Safari 600.1.4

Problem description: When the reference line is over any button / slider / check box on the screen, they are no longer active.

Steps to reproduce: Turn on reference line. Position over any clickable item, attempt to use selected item.

Severity:

Screenshots:

Troubleshooting information (do not edit):
Name: ‪Wave on a String‬
URL: http://www.colorado.edu/physics/phet/dev/html/wave-on-a-string/1.1.0-rc.1/wave-on-a-string_en.html
Version: 1.1.0-rc.1 2016-02-25 18:21:38 UTC
Features missing: fullscreen
User Agent: Mozilla/5.0 (iPad; CPU OS 8_4_1 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) Version/8.0 Mobile/12H321 Safari/600.1.4
Language: en-us
Window: 1024x648
Pixel Ratio: 1/1
WebGL: WebGL 1.0 (OpenGL ES 2.0 IMGSGX543-115.5)
GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.00)
Vendor: WebKit (WebKit WebGL)
Vertex: attribs: 16 varying: 8 uniform: 128
Texture: size: 4096 imageUnits: 8 (vertex: 8, combined: 8)
Max viewport: 4096x4096
OES_texture_float: true
Dependencies JSON: {"assert":{"sha":"7d27130a","branch":"HEAD"},"axon":{"sha":"9457f36a","branch":"HEAD"},"babel":{"sha":"ab2c800b","branch":"master"},"brand":{"sha":"ac9ccaa7","branch":"HEAD"},"chipper":{"sha":"b3a8a3c2","branch":"HEAD"},"dot":{"sha":"da78031b","branch":"HEAD"},"joist":{"sha":"28f51008","branch":"HEAD"},"kite":{"sha":"10ca8bf2","branch":"HEAD"},"phet-core":{"sha":"c48bf320","branch":"HEAD"},"phetcommon":{"sha":"68270b86","branch":"HEAD"},"scenery":{"sha":"b34b4fea","branch":"HEAD"},"scenery-phet":{"sha":"71a9c763","branch":"HEAD"},"sherpa":{"sha":"bb68bbbc","branch":"HEAD"},"sun":{"sha":"2b83e994","branch":"HEAD"},"tandem":{"sha":"2441eec6","branch":"HEAD"},"wave-on-a-string":{"sha":"a0865794","branch":"HEAD"}}

[jonathanolson]

Annoying, but seems as designed (if we keep the reference line in front of the panels).

We could restrict the vertical movement of the reference line so this wouldn't be an issue. Having it behind the panels becomes more complicated (for grabbing it, etc.)

[ariel-phet]

Looking like WOAS needs some revisiting in the future, but we will not currently address this issue, marking priority deferred.