"EA is something you buy" to "EA is something you can build." In this series, we will create a single simple gold (XAUUSD) EA step by step—from blueprint creation to coding, backtesting, avoiding over-optimization, and improvements—by actually doing the work in order. If the "reference edition" that explains the code line by line is a "dictionary of functions," this series is the "story (build log) of completing one project." We will write it so even someone new to programming can follow along. If you read the overall picture in the free e-book 'Introduction to MQL5 Programming' and then read the source skeleton with the free 'MQL5 Learning Programs (Templates),' your understanding will improve significantly. From drawing the blueprint, to the EA's skeleton, to deciding entry conditions and coding them, to stop loss and risk management, to verification with the strategy tester, to avoiding over-optimization (curve fitting), and to the process of improvement—this is a series where you can experience the cycle of "build, verify, fix" with a Gold EA. ※This series is for educational and informational purposes and does not solicit any specific investment actions. The codes included are for learning and do not guarantee profitable trading logic. Verification results are based on historical data for reference and do not guarantee future results.