Have you taken the time to do any of the tutorials? There are no tutorials I know of on the site for your specific game type, but there are a lot of tutorials that will teach how to use the program. Before attempting to make any type of game, you should take the time to learn the mechanics of Construct and study a little bit of game design. Most people who try to dive straight into making any one particular type of game without first learning the basics will wind up frustrated and will never complete any project. That is until taking a step back to learn.
Start Here:
https://www.scirra.com/tutorials/37/beg ... onstruct-2
how-do-i-frequently-asked-questions_t63692
Before attempting this type of game, you will need to learn:
1- how to make an object follow a path
2 - how to rotate an item using mouse input for aiming
3 - how to check and handle collisions
4 - how to trigger events (for example, when the ball train gets to the end of the path, you need to trigger a game over event)
5 - how to insert a new object into a chain of objects (ie when a ball hits the train, it needs to be added where it hits)
6 - how to check for the correct number of same type objects connected (3 red balls in a row)
7 - how to keep score so you can tell when the player has won
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8 - how to create and run animations (you don't technically need sprite animations for this type of game but it makes it look a lot better.
9 - how to add bonus items
10 - how to add sounds (music and/or sound effects)
You can find tutorials that go over many (but not all) of the items listed above by searching the tutorials section on this site. You can also find many good examples built into Construct in the templates.
If you take the time to look learn each of the above (either from examples, tutorials or trial and error) and don't try to skip the learning step, you may just be successful with your project. Just remember, Construct is a tool and if you don't take the time to learn the tool, it doesn't matter how good your idea is.