add more levels and organise them into sections

README.md

@@ -8,6 +8,7 @@ logic mostly like https://git.crispypin.cc/CrispyPin/marble
 story/lore
 timestamps in solutions and blueprints
 multiple input/output sets
+undo/redo
 tooltips
 lock tile types for early levels to make it less overwhelming
 make a gui alternative to pressing R to rotate between tile variants
@@ -79,16 +80,16 @@ blueprint rotation?
 
 ## levels
 ### intro, basic mechanics
-- output a zero
-- output two numbers in sequence
-- output zeroes forever (looping)
-- copy the input
-- copy only odd input numbers
+- output a zero (marble, io)
+- output multiple numbers in sequence (digits)
+- output zeroes forever (looping, trigger, bag output)
+- copy the input (input)
+- copy only odd input numbers (comparator, flipper)
 ### 0-terminated list processing
-- calculate list length
+- calculate list length (math, bag input)
 - count instances of 5 in a list
-- copy the second list (ignore input until first zero)
-- reverse a list
+- copy the second list
+- reverse a list (bouncing)
 ### user-friendly numbers
 - convert a number to decimal ascii
 - parse an ascii number