gistfile1.rb

height = 10
base = [height / 6, 8].max
width = lambda{|r| r * 2 - 1}
to_center = lambda{|s| s.center([height, base].map(&width).max)}
to_stars = '*'.method(:*)
tree = lambda{|v| v.map(&width).map(&to_stars) }

puts (
  tree[1..height] +
  tree[[2]*3] +
  tree[5..base].reverse
).map(&to_center)