Form with input field in modal overlay; also validate user input and show validation feedback
"Start Game" button should clear current game board or "Game Over" message
Turns should switch automatically between the two players, every player has his/her own symbol
Game fields are clickable & the player's symbol is displayed; Check for winner (regular Tic-Tac-Toe rules) after every turn
Present "Game Over" message which highlights winner (or draw) once the game ends