cleanup
rayon
ch 13 done
ch 12 done
ch 11 done
ch 10 done
ch 9 done
ch 8 done
ch 7 done
ch 6 done
ch 6.5 done
ch 6.4 done
ch 6.3 done
ch6.1 done
ch5 done
ch4 done
up to chapter 4