Lyric discussion by SideshowJill 

Cover art for Slide lyrics by Dresden Dolls, The

"her veins are all showing" If you havent hit at least your mid twenties you probably havent notices how those veins tend to rise up. Im pretty sure its about how the "little girl" is aging, not about drug use. "Late April day" when she's at the top of the slide. Spring is a metaphor for youth or being youthful or young" the "orange old man at the bottom" could easily be autumn.

"Past getting Brighter"
When you're in your teens there isnt much of a past. There's your childhood, but when you're a teen you are more of an adult and doing more adult things. When adults look back on their history much of their late teens are included in their adult memories. Maybe the reference is that the past seems much brighter than it might of when you were in it.

/end blather.