To build new metro lines, tap and drag from one station to another. You can change the line's color by tapping on it. Ensure that new lines connect efficiently to existing routes to minimize congestion.

If a station becomes overcrowded, passengers will start to leave. To prevent this, add more trains to the line servicing that station or create new lines to distribute the passenger load more evenly.

Train frequency is managed by the number of trains assigned to a line. You can add more trains by selecting a line and choosing to add trains. Regularly check passenger flow to maintain adequate frequency.

To complete levels efficiently, focus on the following strategies: 1. Develop a balanced network, 2. Anticipate future station placements, 3. Upgrade lines as needed, 4. Monitor passenger flow regularly to adjust services.

Unlocking new maps requires reaching specific milestones in the current map. Each map has a target number of passengers to transport. Once you achieve this goal, you will unlock the next map to play.