create assets for stage 2
create foundation, balanceboard, compound objects
fix bug: create level failed
complete stage 2_1
create stage 2_2
redesign stage 1_1
remove balance board system and refactor object builder
create a builder for broom
create debug mode
move foundation and balanceboard to special object builder
create stage builder
Refactor Stage Engine
create dialog builder. PS: tutorial stage1_1 is broken
fix broken tutorial
readjust score points. BUG: lose condition failed
fix bug and clean up code
create stage 2-3
fix bug: lose condition failed
clean up DraggableObject
add missing import