Add a draft about digit sum patterns.

code/patterns/patterns.rb

@@ -0,0 +1,68 @@
+require 'victor'
+
+def sum_digits(n)
+  while n > 9
+    n = n.to_s.chars.map(&:to_i).sum
+  end
+  n
+end
+
+def step(x, y, n, dir)
+  case dir
+  when :top
+    return [x,y+n,:right]
+  when :right
+    return [x+n,y,:bottom]
+  when :bottom
+    return [x,y-n,:left]
+  when :left
+    return [x-n,y,:top]
+  end
+end
+
+def run_number(number)
+  counter = 1
+  x, y, dir = 0, 0, :top
+  line_stack = [[0,0]]
+
+  loop do
+    x, y, dir = step(x,y, sum_digits(counter*number), dir)
+    line_stack << [x,y]
+    counter += 1
+    break if x == 0 && y == 0
+  end
+  return make_svg(line_stack)
+end
+
+def make_svg(line_stack)
+  line_length = 20
+  xs = line_stack.map { |c| c[0] }
+  ys = line_stack.map { |c| c[1] }
+  
+  x_offset = -xs.min
+  y_offset = -ys.min
+  svg_coords = ->(p) {
+    nx, ny = p
+    [(nx+x_offset)*line_length + line_length/2, (ny+y_offset)*line_length + line_length/2]
+  }
+  
+  max_width = (xs.max - xs.min).abs * line_length + line_length
+  max_height = (ys.max - ys.min).abs * line_length + line_length
+  svg = Victor::SVG.new width: max_width, height: max_height
+  
+  style = { stroke: 'black', stroke_width: 5 }
+  svg.build do
+    line_stack.each_cons(2) do |pair|
+      p1, p2 = pair
+      x1, y1 = svg_coords.call(p1)
+      x2, y2 = svg_coords.call(p2)
+      line x1: x1, y1: y1, x2: x2, y2: y2, style: style
+      circle cx: x2, cy: y2, r: line_length/6, style: style, fill: 'black'
+    end
+  end
+  return svg
+end
+
+(1..9).each do |i|
+  run_number(i).save "pattern_#{i}"
+end