update todo

README.md

@@ -13,9 +13,10 @@ https://www.linuxhowtos.org/C_C++/socket.htm
 * [x] waits for connection
 * [x] send a message to the client
 * [x] move core rendering out of main.cpp
-* [ ] combine 'hittable' 'hittable_list' and 'scene' into 'world'
+* [x] combine 'hittable' 'hittable_list' and 'scene' in 'world'
 * [x] send rendered image data to client
 * [x] form image file on client
+* [ ] extract netcode from main
 * [ ] specify protocol format
 * [ ] receive imaging command
 * [x] render image