"Physics engine" in the terminal (https://vimeo.com/146376459)

terminal_physics_engine.rb

require 'io/console'
puts"\e[?25l\e[?1000h";at_exit{puts"\e[?25h\e[?1000l"} # no cursor, yes mouse
x = y = dy = ax = ay = 0; dy = dx = 0.5
height, width = $>.winsize
def hot_cold(name, val)
  index = (3*Math.tanh(val)).to_i+2
  "\e[38;5;16m" << [{r:5},{r:5,g:2},{r:4,g:4},{g:3,b:4},{b:5}]
                     .map{ |r:0,g:0,b:0| "\e[48;5;#{r*36+g*6+b+16}m" }
                     .map.with_index{|c,i| c+(i==index ? name : "-") }
                     .join <<
                   "\e[40;37m %6.2f"%val
end
done = false
fg   = 7
Thread.new{$stdin.raw{
  until done
    case c=$stdin.readpartial(20)
    when "\e[A" then    ay -= 0.1 # arrow keys change acceleration
    when "\e[B" then    ay += 0.1
    when "\e[C" then    ax += 0.1
    when "\e[D" then    ax -= 0.1
    when 3.chr  then    done = true # C-c kills program
    when /\e\[M (.)(.)/ # mouse down
                        dx,dy,x,y = 0,0,*[$1,$2].map { |n| n.force_encoding(Encoding::ASCII_8BIT).ord-32 }
    when /^\d/   then   fg = $&
    end
  end
}}
until done
  sleep 0.05
  # multipliers are to make the change less volatile
  dx += ax*0.1 # apply x acceleration
  dy += ay*0.1 # apply y acceleration
  x  += dx/2   # apply x velocity
  y  += dy/2   # apply y velocity
  # Detect wall collisions. I think this probably requires consideration of how long they are in contact
  # and what kind of material they are, but thats more real than I care to get with it
  y,dy = y<1 ? [1,-dy*0.8] : y>height  ? [height, -dy*0.8] : [y,dy]
  x,dx = x<1 ? [1,-dx*0.8] : x+1>width ? [width-2,-dx*0.8] : [x,dx]
  print "\e[40m\e[H\e[2J"                 << # reset
        hot_cold(?x,dx)+" x-velocity\r\n" <<
        hot_cold(?y,dy)+" y-velocity\r\n" <<
        hot_cold(?x,ax)+" x-accel\r\n"    <<
        hot_cold(?y,ay)+" y-accel"        <<
        "\e[%d;%dH\e[4#{fg}m  "%[y.to_i,x.to_i]  # ball
end