Due to the proliferation of technology in daily life and the growing number of ways in which humans and machines interact, the process of designing interactive elements has become critical. Nevertheless, design students are seldom able to design and implement interactive elements because of their limited programming skills. Although there have been some approaches to teach computational thinking using physical computing and focusing on solving real-world problems (e.g., electronic devices such as Arduino, using sensors and actuators), they often entail monetary expenses and require knowledgeable instructors, and are not catered to students without prior programming or electronics knowledge. Hence, we propose the use of Protobject, a low-cost tool that focuses on real-world applications that could be used to teach programming to design students. This study aims to evaluate students' perceptions regarding the usability of Protobject as a tool for learning computational thinking, as well as the clarity of the learning activities designed to teach computational thinking concepts by using Protobject.