Shows circles around the screen with ruby Curses' console interface.

circle.rb

require 'curses'

# Hell yeah
DANI_NUMERO_CIRCULOS = 4
DANI_LIMPAR_TELA = false


# All possible colors.
Colors = {
  :black   => 1,
  :white   => 2,
  :red     => 3,
  :yellow  => 4,
  :magenta => 5,
  :blue    => 6,
  :green   => 7,
  :cyan    => 8
}.freeze

# Starts curses terminal-handling library with all of it's colors.
def init_curses
  Curses::init_screen
  Curses::start_color
  Curses::init_pair(Colors[:black],   Curses::COLOR_BLACK,   Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:white],   Curses::COLOR_WHITE,   Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:red],     Curses::COLOR_RED,     Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:yellow],  Curses::COLOR_YELLOW,  Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:magenta], Curses::COLOR_MAGENTA, Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:blue],    Curses::COLOR_BLUE,    Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:green],   Curses::COLOR_GREEN,   Curses::COLOR_BLACK)
  Curses::init_pair(Colors[:cyan],    Curses::COLOR_CYAN,    Curses::COLOR_BLACK)
  Curses::noecho
  Curses::curs_set 0
end

# Executes a block of code encapsulated within a color on/off.
# Note that the color can be overrided
def with_color color=nil
  Curses::attron(Curses::color_pair color) if (color != nil)
  yield
  Curses::attroff(Curses::color_pair color) if (color != nil)
end

# Puts a character `c` on (`x`, `y`) with optional `color`.
def mvaddch x, y, c, color=nil
  return if x < 0 or x >= Curses::cols
  return if y < 0 or y >= Curses::lines

  with_color color do
    Curses::setpos(y, x)
    Curses::addch c
  end
end

# Puts a string `str` on (`x`, `y`) with optional `color`.
def mvaddstr x, y, str, color=nil
  return if x < 0 or x >= Curses::cols
  return if y < 0 or y >= Curses::lines

  with_color color do
    Curses::setpos(y, x)
    Curses::addstr str
  end
end

# Puts a string `str` centered on `y` with optional `color`.
def mvaddstr_center y, str, color=nil
  x = (Curses::cols/2) - (str.length/2)
  mvaddstr x, y, str, color
end

class Circle
  attr_accessor :x, :y, :radius, :char, :color

  def initialize(x, y, radius)
    @x = x
    @y = y
    @radius = radius
  end

  # Shows the circle on the screen
  def print
    return if (@x + @radius) > Curses::cols # avoiding infinity

    angle = 0.01
    angle_step = 1.0/@radius

    while angle < (2 * Math::PI)
      cur_x = @radius * Math.cos(angle)
      cur_y = @radius * Math.sin(angle)

      mvaddch(@x + cur_x, @y + cur_y, @char, @color)
      angle += angle_step
    end
  end
end

# A container that spawns random circles with random colors at
# random positions with random radius sizes and random growth
# rates
class CircleContainer

  def initialize
    @circles = []
  end

  # Inserts a circle.
  def add
    circle = Circle.new(Random.new.rand(0..Curses::cols-1),
                        Random.new.rand(0..Curses::lines-1),
                        Random.new.rand(0..3))

    circle.char = ['.', '*', '#'].sample # random array element
    circle.color = Colors.to_a.sample[1] # random hask element

    @circles.push circle
  end

  # Updates all circles.
  def update
    for i in 0..(@circles.length-1)
      @circles[i].radius += 1
    end
  end

  # Prints all circles.
  def print
    Curses::clear if DANI_LIMPAR_TELA
    for i in 0..(@circles.length-1)
      @circles[i].print
    end
    Curses::doupdate
  end
end

# This is where the fun begins.
begin
  init_curses

  mvaddstr_center 1, "Wave", Colors[:red]
  mvaddstr_center 2, "y = Asin(kx - wt - y) + D", Colors[:yellow]

  circles = CircleContainer.new
  for i in 0..DANI_NUMERO_CIRCULOS
      circles.add
  end

  while true
    circles.update
    circles.print
    Curses::refresh
    sleep 0.03
  end

  Curses::getch
end