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The last two decades have witnessed significant advances in the field of indoor positioning systems, which have led to technologies with high location precision. However, there still lacks robust meter-level indoor positioning approaches which only rely on in-building communication infrastructures and smartphones. We present STARLIT, a system that enables a single LED beacon to localize smartphones to within sub-meter. As the smartphone camera contains millions of pixels, we create a virtual sensor array with the camera to measure the received signal strength (RSS) of the LED beacon. Different from the existing camera-based approaches, which need to capture images of the LED within a short light-to-camera distance, we utilize the reflection light from the floor. By exploiting the rolling shutter mechanism in the smartphone cameras, we propose a solution to separate the signal layer from the image background and noise. Given the measured RSSs, we establish an equation set with the Lambertian model and the camera projection model to solve the location of the smartphone. We have implemented STARLIT and evaluated its performance in an office room. Our experiments demonstrate that the STARLIT can achieve a median error of 23cm and an 80-percentile error of 55cm.