Can We Prevent "Text Neck" Using Only a Smartphone? Real-Time Neck Angle Estimation and a Serious Game as a Case Study

Prolonged smartphone use often results in forward head posture, commonly known as "text neck," which places excessive strain on the cervical spine and may lead to various health problems. However, users typically find it difficult to monitor and correct their posture without external support. To address this challenge, we propose a method for real-time neck angle estimation using only a smartphone’s front-facing camera and built-in sensors. Our approach extracts posture-related features such as the normalized distance from the nose to the neck base, interocular distance, smartphone tilt, and facial orientation. Regression analysis using Random Forest and Extra Trees models indicates that neck angle can be estimated with moderate accuracy (for example, 𝑅2 ≈ 0.6 and MAE ≈ 8.5◦), although performance at extreme angles remains limited. To evaluate the practical utility of this system, we developed a serious game titled Look Up and Tap! that provides real-time visual feedback, including screen contrast adjustment and button highlighting, based on the estimated neck angle. A user study with 10 participants showed that this feedback significantly improved users’ awareness of their posture and encouraged more upright neck positions. These findings suggest that neck angle estimation using only a smartphone is feasible and can help promote posture awareness in everyday settings. The serious game serves as one example of how this approach can be applied in real-world scenarios.