Push atoms into the answer box

[KatieWoe]

Test device
Dell
Operating System
Win 10
Browser
Chrome
Problem description
Found in https://phet-dev.colorado.edu/html/build-a-molecule/0.0.0-dev.28/phet/build-a-molecule_en_phet.html?dev while testing fixed issues. Fairly minor. It is possible to push atoms into the answer area even though they would normally be pushed out.
Steps to reproduce

1. Make part of a molecule
2. Put it beside the answer box
3. Cut the molecule apart

Visuals

Troubleshooting information:

!!!!! DO NOT EDIT !!!!!
Name: ‪Build a Molecule‬
URL: https://phet-dev.colorado.edu/html/build-a-molecule/0.0.0-dev.28/phet/build-a-molecule_en_phet.html?dev
Version: 0.0.0-dev.28 2019-12-05 16:25:33 UTC
Features missing: touch
Flags: pixelRatioScaling
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36
Language: en-US
Window: 1536x722
Pixel Ratio: 2.5/1
WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium)
GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium)
Vendor: WebKit (WebKit WebGL)
Vertex: attribs: 16 varying: 30 uniform: 4096
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 32767x32767
OES_texture_float: true
Dependencies JSON: {}

[Denz1994]

Related to #120

[Denz1994]

This may have been corrected due to changing play area bounds in #120. Can you confirm this isn't an issue in this dev version @KatieWoe?

[KatieWoe]

This does seem fixed, but I noticed that the molecules move back to the play area in two disjointed steps.

[Denz1994]

Right this disjointed action is due to using both the kit.separationMoleculeDestinations() and Twixt animation support. We can get away with using just the Kit's model to handle the bounds for the molecules along with constraining them to those kit bounds.

I removed support for the animation behavior so we are solely relying on kit.js to do this for us.

The behavior has been updated in this dev version. Can you review @KatieWoe?

[loganbraywork]

Appears to be fixed

[Denz1994]

Nice closing this one.