Vulnerabilities in smart contracts on the Ethereum platform attract significant attention from both the scientific and professional communities due to their potential to cause substantial financial losses. Among these, the reentrancy attack is particularly notorious for its ability to manipulate the execution flow and reactivate vulnerable functions within a smart contract, thereby disrupting intended operations and causing damage through unforeseen actions. This work aims to systematize, simplify, visualize, and extend existing knowledge on this topic. A thorough analysis of the 'Single-Function Reentrancy Attack' is conducted, during which various defense methods are meticulously investigated and systematically organized. The research methodology encompasses a literature review, code analysis of vulnerable and attacking contracts, and testing on models adapted for this paper. An important aspect of this paper is its focus on the practical testing and understanding of vulnerabilities, allowing readers to verify the experiments and validate the results independently. The examination of the implementation of vulnerable and attackable contracts reveals subtle aspects of code execution flow on the Ethereum Virtual Machine, enhanced by visual aids. This paper offers a unique analytical perspective and emphasizes the necessity of continuous analysis and updating of security strategies, as well as the development of new security tools, including automated solutions, to keep pace with rapidly evolving threats.