add review comment, see #165

doc/model.md

@@ -37,11 +37,11 @@ for protons and neutrons.
 In the Build a Nucleus simulation, a user can build a nuclide from protons and neutrons. The nuclide is assumed to be
 neutral since the electron cloud contains as many electrons as there are protons.
 
-The user can place neutrons and protons into the play area either by using the spinners next to the nucleons. The
-spinner between the protons and neutrons places both a proton and neutron into the nucleus simultaneously.
-Nucleons can also be placed by dragging them into the nucleus in the **Decay screen**, or dragging them into the energy
-levels play area in the **Chart Intro screen**. If a nucleon particle is placed outside the play area, it will return to
-its stack.
+The user can place neutrons and protons into the play area by using the spinners next to the nucleons. The spinner
+between the protons and neutrons places both a proton and neutron into the nucleus simultaneously. Nucleons can also be
+placed by dragging them into the nucleus in the **Decay screen**, or dragging them into the energy levels play area in
+the **Chart Intro screen**. If a nucleon particle is placed outside the play area, it will return to its stack.
+<!--- REVIEW: I'm not seeing anything that looks like a "stack" in the sim.  Does this reference need an update? -->
 
 As the number of nucleons in the nucleus changes, the sim updates the nuclide species name (eg. Helium-5) and the
 readout of nucleon numbers. Only nuclides that exist on Earth can be built, this is done through the disabling of