How to have an invisible boundary

I want to make a game that you draw a line and roll a ball down, how do you make it so you cant draw the line any further? but the boll can still roll down?
Thanks. [import]uid: 23689 topic_id: 8243 reply_id: 308243[/import]

Can you give some more details, please?

Is the boundary only on Y or X, or is it like a box?

Also, is the line straight?

Peach :slight_smile: [import]uid: 10144 topic_id: 8243 reply_id: 30958[/import]