todo

field example
######################################################
#01 *****                                            #
#02                                                  #
#03                                                  #
#04                                                  #
#05                                                  #
#06                                                  #
#07                                                  #
#08                                                  #
#09                                                  #
#XX                                          %       #
###0        1         2         3         4         5#
###12345678901234567890123456789012345678901234567890#

moving invaders
- if collision with wall -> move down & inverse direction

defender shooting
- respect invaders + old darts on last row
- moving darts up
- detect colision
- removing invader + dart if colision


aliens shooting
detecting if invaders invaded our realm

put all pieces together

make a real quine 
- be sure to write to the source file


moving invaders right moves invaders right