Code quality is a constant challenge faced by today's software industry. To ensure that developers follow good coding practices, a variety of program analysis and test coverage tools are routinely deployed. However, these tools often fail to engage and change the practices of developers when applied to legacy systems as they output a huge number of warnings, quickly overwhelming the developers. In this article, we explore how individual feedback and gamification can motivate developers to pay more attention to good coding practices. To that extent, we implemented these two concepts in a tool that we deployed at two large companies where we conducted a case study. We find out that individual feedback is essential for motivating developers. We also find that gamification can be useful but has to be used with caution as it can frustrate some developers. Finally, we reflect on some lessons learned during our case studies and conclude that the promising approach of our tool needs to be supported by longitudinal studies as well as comparative studies.