Swipe left/right or use left/right keyboard arrows to change letters
Swipe up/down or use up/down keyboard arrows to make letters smaller or larger
Type the distance you want to hold the screen at (in cm), default 1.5m
Chose from the device dropdown to auto set the scale or calibrate as below
To calibrate the scale: Double click "fix" and type in the actual size of the letter on the screen (in cm)
the system will then correctly size the chart for your device
After calibrating, consider sending the correct scale for your device here so others can use it
Tap the score eg. "6/60" to save
Your defaults will be saved to your cookies for 1 year