StarBall

StarBall is a two-dimensional interception game built to answer a deceptively simple question: when we catch something moving, are we reacting to what we see — or predicting what we can't?

The Game

Players control a paddle with the mouse, moving it horizontally to intercept a ball falling from the top of the screen. Across trials, four factors are systematically manipulated: the ball's velocity, whether it obeys normal gravity (1g) or a artificial zero-gravity trajectory (0g), whether its flight path is briefly hidden behind an occluding panel, and whether the ball and paddle start on the same or opposite sides of the screen. Every mouse and paddle movement is recorded at high temporal resolution, allowing the full trajectory of each catch — not just its success or failure — to be analyzed.

Research Questions

• Do people intercept moving targets by reacting to what they currently see, or by predicting where the target will be?
• When the target's motion is hidden, do people fall back on a generic guess — or do they extrapolate its trajectory as if it still obeyed Earth's gravity, even when it doesn't?
• Does this predictive strategy stay fixed, or does it flexibly adapt depending on target speed, visibility, and the spatial layout of the task?

The results show that interception is largely predictive rather than purely reactive: players consistently move the paddle ahead of the ball rather than simply tracking it. Strikingly, when a ball's path is hidden under zero-gravity, players behave as though it still falls under normal gravity — revealing a built-in physical prior that persists even when it leads them astray. This flexible, prediction-based strategy sits at the center of my broader research on embodied decision-making.