This was the first Ivy puzzle I made. In terms of difficulty, I think it’s also a good introduction to the genre, but you’ll find that the solution has a property that makes it not ideal as an example puzzle.
Rules: Draw a connected network of branching lines through the centres of some cells without forming any 4-way intersections or closed loops. Every endpoint is marked with a number, and every number marks an endpoint, indicating the total line length from the endpoint to the nearest branch point.