Academically, I think I got in because I basically ended up dedicating my entire four years of high school to my STEM-related field. I received special leeway from my school and took most of my classes via dual enrollment, self-study for credit, or credit from hands on experience in the field. None were options at my school previously, but my school district was awesome and let me personalize my education to the point that I was a mini-expert and had received a few national and international awards in the field when I graduated. I was insecure though because I basically neglected the other subjects that didn't interest me, and although I did "well" in them, I didn't feel like I was at "Harvard level" in them compared to my field. Looking back at it now, this wasn't as big of a problem as I thought, but it was hard when comparing myself to those that seemed to be perfect at everything. ECs were the biggest factor in my acceptance, I think, as many admissions officers highlighted a very unique EC that I did on a national level that was completely unrelated to STEM. This EC helped give me the personal factor and make me human which helped me stand out from other people interested in my field. I think the key is making the case as to why you are different than every other person pursuing that field or that EC.