changes made:
changes made:

turn the screen to the right by doing a switch of the i and j arrays
made intensity graph and envelope work in the right panel
scale the y to fix the 1 m instead of the older 200
added a scale factor to make the display coincident with the other applet made by andrew duffy
added source as triangle of laser
added ? slider with color indicated by adding colorlookang codes
set default as double slit N = 2, the open input field technically allows for multiple slits up to 20 as previously designed by Fu-Kwun Hwang
made a, d, L and y
made intensity and different from the envelope
redesign the layout to suit left to right with right panel showing the screen
laser redrawn
added background
slits added
text of views added
added point yp with reference made to tat leong yp
made the codes work under the new design space of x = -0.5,1 and y = -1 and 1