```ruby
class MiniMetro < Cask
  url 'http://static.dinopoloclub.com/minimetro/builds/alpha12/MiniMetro-alpha12a-osx.zip'
  homepage 'http://dinopoloclub.com/minimetro/'
  version 'Alpha 12a'
  sha256 'cbbf5e60c39bb4d850e65703e220d41a0410212fc6f87d997abe36dc2d7658f9'
  link 'MiniMetro-alpha12a-osx.app', :target => 'Mini Metro.app'
end
```

Update Mini Metro to alpha 13b
user
```ruby
class MiniMetro < Cask
  url 'http://static.dinopoloclub.com/minimetro/builds/alpha13/MiniMetro-alpha13b-osx.zip'
  homepage 'http://dinopoloclub.com/minimetro/'
  version 'Alpha 13b'
  sha256 '77416668bc5c2a982642cb692b35b7f0b5854cb950750477aa6d362d2b68246b'
  link 'MiniMetro-alpha13b-osx.app', :target => 'Mini Metro.app'
end
```
assistant