Ok, so we already have glass walls, windows, ceilings and floors.
Stage 1 (existing): use glass ceilings/floors to allow sunlight downward to prevent dwarfish cave adaptation.
Stage 2: Toady adds light pathing to the DF physics engine. Mirrors (glass + silver) can be created at a glass forge. A new building type "light channel" (glass blocks + mirrors) channels different qualities of photons (green, clear or crystal clear) around corners underground. Green light is sufficient for cave adaptation and growing some above-ground crops. clear glass grows finicky light loving crops underground.
Stage 3: Weaponizing light. New buildings 'Solar mirror' (mirror + mechanism), built on the surface, follows the sun and directs intense light into light channels. Light can be used to generate power (solar steam engine; modified from magma steam engine). It can also be used to melt metal (solar furnace; modified from magma furnace) or forge metal items (solar forge; modified from magma forge). New safety clothing (smoky glass helm/goggles) would be required, except that dwarves refuse to wear safety equipment; it offend their fashion sense and won't fit over their helms. Players discover that high intensity light can melt ice, stun underground cave adapted monsters, vaporize vampires, and possibly weaken clowns. Can you say "DF death laser" without giggling?
DF light could lead to a wave of retrofitting older forts and new mega-projects by jaded DF players.
No thanks are needed. Just doing my small part to delay the DF interface for another generation --Targetdroid
Targetdroid has recently enjoyed a soapy bath. He feels satisfied at work. He was gloomy after being out in the sunshine again. He felt fondness at talking with a friend. He is a member of the Bay12 forums. He has no beard but is often unshaven. His brown curly hair is combed back neatly. His eyes are green. He is very rarely sick, is agile, and quite strong, but he is quick to tire. He likes agate, gauntlets, oak quarter staves, sad songs, the color blue, computer games for their complexity, and cats for their beauty and aloofness. He absolutely detests slugs and mosquitos. When possible he likes to consume cow cheese, Indian cuisine, pizza, and dark beer. He has good creativity, great analytical ability, but a questionable memory. He holds craftsdwarfship to be one of the highest ideals and celebrates talented artisans and their masterworks, greatly prizes loyalty, values family greatly, sees friendship as one of the finer things in life, believes that honesty is a high ideal, really respects those who take time to master a skill, values cooperation, values martial prowess and has a tendency to form deep emotional bonds with others. He values self-control, sees introspection as important, and deeply respects those that work hard at their labors. He dreams of creating a great work of art. He is quite comfortable with others that have a different appearance or culture. He is often sad and dejected. He is an optimist. He tends to be a little tight with resources when working on projects. He has an active imagination. He doesn't cling tightly to ideas and is open to changing his mind. He generally acts with a narrow focus on the current activity. He can handle stress. He has a calm demeanor. He finds helping others emotionally rewarding. He prefers that everyone live as harmoniously as possible. He tends to avoid physical confrontations and he works to square this with his love for martial prowess. He needs coffee to get through the working day. he likes working outdoors and grumbles only mildly at inclement weather. A short, sturdy creature fond of drink and industry.