triangles is a mapping/storyboarding contest bolstering lazer's theme song cYsmix - triangles! Check out the introductory news post for contest details, the voting news post for voting information, as well as the wiki article for the most up-to-date info.
Vote for this contest by playing any of the triangles playlists in osu!(lazer). More specifically, you're required to play at least one difficulty from each mapset, and those plays can be spread across different playlists.
Access the playlists via the play menu on osu!(lazer) and filtering by Featured Artists in the top-right corner. There's one playlist for each difficulty level (Easy/Normal/Hard/Insane/Expert).