WinStrategy implemented
Defence strategy implemented
Invincible Opponent receives a list of strategies
Invincible player starts the game
FirstEmptyCellStrategy implemented
Corner strategy initial implementation
Tests for CornerStrategy
Board and Marks inform when they are full
Draw message
marks array removed from Board
marks array removed from Board
Marks passed into BoardLines
Marks passed as parameter to Line
Marks as array passed to BoardDisplay
Minor refactoring
Opponent interface removed
Opponent interface removed
Line refactoring
Package structure introduced
Single player functionality removed