SPARC is a research application designed to understand to young adults' substance use and other health behaviors. The iPhone app supports the Apple Watch app, which is what participants primarily interact with. The study, protocols, and the use of these applications by eligible participants is approved by Pennsylvania State University's Institutional Review Board (IRB Number: STUDY00013672). Eligible participants will use the watch app for a designated amount of time, where they are able to answer survey questions about various health behaviors, experiences, and contexts. Participants are also asked to share their Health data through Apple's Health app, and their location data. Sharing this data is entirely voluntary and participants may choose not to, and have full control over the types and amount of Health and Location data they can share with the app.