update todo list, print real time taken when level is completed

README.md

@@ -4,19 +4,20 @@
 logic mostly like https://git.crispypin.cc/CrispyPin/marble
 
 ## todo
-(more levels)
-story/lore
-copy/cut/paste selections
-timestamps in solutions and blueprints
-multiple input/output sets
-undo/redo
-tooltips
-show level info in editor
-lock tile types for early levels to make it less overwhelming
-display tool variant more clearly (it's not obvious there are more states)
-make marble movement more consistent (`>o o<` depends on internal marble order)
-decide on marble data size (u32 or byte?)
-blueprint rotation?
+- copy/cut/paste selections
+- undo/redo
+- more levels
+- make marble movement symmetric and order-independent
+- make power propagation not recursive
+- story/lore
+- timestamps in solutions and blueprints
+- multiple input/output sets
+- tooltips
+- show level info in editor
+- lock tile types for early levels to make it less overwhelming
+- display tool variant more clearly (it's not obvious there are more states)
+- option to use 8-bit marbles?
+- blueprint rotation?
 
 ## file hierarchy
 ```