PrepCity is an AI interviewer that never goes easy on you. It catches bad math, challenges vague answers, and grades you on Google's L3-L7 scale. For coding, it derives solutions from observation - not memorization. Trace by hand, spot the pattern, code emerges naturally. For system design, it analyzes your architecture with graph algorithms to find flaws, then grills you on each one. Web, Android, Windows. Voice mode included. 236 topics. 74 coding problems.