Every student needs feedback to understand a scientific concept deeply. However, with a large number of students in each class, individual feedback is a challenge for teachers in Indonesia. Although there have been many studies conducted to maximize the giving of personal feedback, studies conducted by ensuring the consistency of a student's knowledge of a concept before providing feedback are rarely disclosed. This study aims to develop computer-assisted formative feedback (CAFF) based on students' cognitive resources. Besides, this study also intends to determine student perceptions related to the use of CAFF. This current study involved two experts as advisers in the development process and 31 high school students who acted as participants in the pilot phase. CAFF could identify the students' cognitive resources and then provided interactive feedback to students based on it. Therefore, it will be beneficial to associate students' prior knowledge with scientific concepts. Instead of giving feedback by showing whether or not students' answers are correct, displaying the exact concept text, or providing general instructions to the right concept, CAFF presents feedback by showing students' cognitive resources followed by the interactive explanation associated with specific cognitive resources. Students shared positive perceptions about the program. Cognitive resource diagnoses and forms of feedback in the CAFF model can be further developed on more nuanced topics.