Merge pull request #48 from winstonho/master

update
update collision
Merge pull request #49 from winstonho/master

update collision
update
Merge pull request #19 from huanzhz/master

m49
resize
Merge pull request #50 from winstonho/master

update
update
Merge pull request #20 from huanzhz/master

ai m
ai is in
Merge pull request #33 from winstonho/master

AI is place at they