Educational computer-based competition environments need to be designed with a set of features that enhance the learning process. Although recently some frameworks for the design of educational computer-based systems (e.g., educational games) have been proposed, they do not focus on the details of the competition. Therefore, the design of educational computer-based competition environments is still an open issue. We propose the 4NESS framework for the design of such competition environments. This framework classifies the competition features into four dimensions: easiness, fairness, awareness, and adaptiveness. We designed the ISCARE educational computer-based competition environment implementing these four dimensions to evaluate and validate some included features for competition, and conducted experiments during three consecutive years. Students considered the computer-based competition environment with the proposed features, including a modification of the Swiss system, to be very easy to use, fair for pairing students, moderately fair for calculating scores, with good awareness of their state during the competition and that of their peers, and with contents of appropriate level, especially for the group working with adaptive contents. Adaptation of contents made students increase their learning gains in 0.5 sigmas during the competition. Pairings were seen as with students of similar levels. And final scores were moderately fair: while the order tends to be similar as compared to the results in the post-test, students grades with high performance tend to be lower in the competition environment.