how 2 desingn a Mobile robot collecting a golf-balls?

Hello guys

i have a project(20%) in my mechatronics system design subject, i have to build a golf-ball collecting robot through a hole goals...there will be a competition among my classemates....and the rules as follows:

game area will be 100cm x 100cm with a wooden fence with a height of 10cm. there will be 20 golf balls in the field. An opening of 15cm will act as the goal mouth located at the center of one end. The game area will be white with black lines (insulation tape) on it 10cm apart making small squares. The robot dimensions are limited to 25cm x 25cm x 25cm.

The task of the robot is to collect as many golf balls and place it in the goal. For each game, the team will be given 3 trials of 2 minute each. Each golf ball represents 1 mark for the team. The highest score obtained by each team will be their carry marks. This way, the marks represent the effort the student put into the project and not just by luck winning or loosing the game. This will give every team equal chance to perform up to their ability.

However, if there is still a need to find a sole winner, I suggest having a league where teams are divided into groups of 3 or 4. Each team will still have 3 tries. The points for all 3 tries are accumulated and the top 2 teams with the most points will then proceed to the knock out stage. If there is a draw between two teams, the team who completes the task the fastest will be considered the winner.

so i dnt have any idea from where i can start...plz i need ur suggestions....thnx