'Earths Last Year: 1999' is a heartwarming slice-of-life dating sim/romance visual novel, with the flavor this time being that it's the Y2K scare, and why not sex your friends if it's the end of the world. Especially for a game jam time frame, getting two different routes done for one of these classic romantic 'pick-a-husbando' is quite good. I really enjoyed the custom art, they brought forth the emotional expressions and there's even art within art, with the custom graffiti scene, and I always find that charming. Props for doing two sex scenes, I thought they were both very hot, and you gave them each their own distinct vibe (the traditional doggy style in a bed and the kinky blowjob in the back alley). I think you achieved what you set out to do with this prompt and premise, especially with how you've incorporated the game jam theme into the ticking clock that moves the plot forward. The characters each were distinct and had their own voices, Flare being the gruff realist, and Cream being the rebellious idealist.
If I were to give any critique, I think you could've squeezed in a bit more establishing the scene prior to the branching path, since you only really learn about Cedar's friendship to each of them once you're properly in their routes. Cream's route also kind of comes off across as a little bit melodramatic, but I can forgive that for this type of story. All the characters are really pleasant, so don't be afraid to give them some rough edges. Also, I think because you've chose such a classic framework for the story, you've expected the reader to come in with a lot of pre-conceived details, like, how Cedar's gay for his friends/they're gay for Cedar but they haven't made any moves in order to not risk the friendship. The idea that because there's this countdown clock till the end of the world is what spurs them to take that risk, but there should be some kind of scene to show just what it is they're risking. As a tip for these type of route based stories, if you're going to do a self-insert type of character like Cedar, try to include a couple of flavor choices to help get the player immersed into the character. Like, say with Flare he asks you what you want for dinner, or with Cream what detail you add to the graffiti. If Cedar is his own character, be sure to have his personality come out a bit, with clear points of view, goals and motivations. Also, the vanilla sex is great, thanks for not shying away from it, really fun detail about reaching climax right as it hits midnight (and that Cedar's got them white undies). Lookin' forward to how you branch out with your future VN projects.