8-24-2007: Centered transition on middle of energy level graphic, not bottom. 8-23-2007: added snap-to feature for setting photon wavelength 8-23-2007: fixed a bug on the first panel. If I have two energy levels and move the 2nd level down to the energy that the 1st level starts by default, then the number on the 2nd level changes to 1. The atom in the play area still has the appropriate level number indicated when it's excited. 8-23-2007: Added snap-to feature for dragged energy level 8-23-2007: Made energy level sliders smaller in vertical direction. 8-23-2007: Improved match graphic. 8-20-2007: Switched tabs to PhetTabbedPane 8-20-2007: Changed tab names to “One Atom (Absorption and Emission)” and “Multiple Atoms (Lasing)” 8-20-2007: Changed actual image from PNG (300kb) to JPG (100kb) 8-20-2007: Increased the range under which absorption is possible by a factor of 5. 8-20-2007: Changed the display for a matching wavelength from "flashes 5 times" to solid bumps (not flashing) 7-5-2007: Fixed: Can move energy level up off the screen and lose it (in current version, it’s constrained to not move this far).