D-2

v-2.3.0
---
1. draw => 1 rectangular

	==> done
D-2

v-2.3.1
---
1. draw => 2 rectangulars

	==> done
D-2

v-2.4.0
---
1. detect => which object the point is located

	==> done for --> Rect A
Merge branch 'D-2_use-canvas'