Fix to challenege sections stomping on freebie sections.
Merge branch 'master' of github.com:redbluestudios/game-off-2013
Merge branch 'master' of github.com:redbluestudios/game-off-2013
Added shield effect and animations for idle and weak shields.
Shield upgrade added to store.
Fixed upgrade bug -- incorrect string name for shield upgrade.
Green Power duration upgrade added.
Merge branch 'master' of github.com:redbluestudios/game-off-2013
Merge branch 'green-power'
Sync up scenes with latest green power changes.