Shard Reader
A Spritz-style RSVP reader for Android. Words appear one at a time at a fixed point, with the anchor letter highlighted — the detail almost no implementation gets right.
The detail that matters
RSVP reading shows one word at a time in a fixed position, eliminating the eye’s saccadic movement. It only works if the eye never has to search for where to look, and for that the word must be aligned by its ORP (Optimal Recognition Point): the point at which the brain recognises it, which is not the centre but slightly to the left, and which depends on word length.
Most implementations centre the word and highlight a letter. That makes the anchor point move between words — exactly what RSVP is trying to avoid.
Here the ORP is pinned at 38% of the screen width and words are positioned around it. The eye never moves.
Other decisions
Variable pacing per token. A seven-letter word does not need the same time as “of”, and a comma
deserves a pause. The delayFactor is computed per token from length and punctuation, and it is
covered by tests.
Explicitly requesting 120 Hz. Android does not hand you the high refresh rate just because the device supports it — you have to ask. In an interface whose only job is swapping text at precise intervals, the difference shows.