I hope you are all doing fine.
We would like to build an app and then I found Invision, which helps us to set up an prototype. Invision then recommends to download the plugin Craft.
Now we would have the following questions:
1. Do we need photoshop or sketch in order to install/ use craft?
2. If yes, what would you recommend us, if we don't have (and won't have) photoshop or sketch? Is there any good alternative software which we can use for setting up a prototype?
Thank you very much in advance for any comments.