The Tidey display 'fills up' with light to indicate low to high tide. When tide is fully out all the lights are off, and when the tide is in all the lights are illuminated.
You can estimate tide time by counting the squares - each little square represents about 6 minutes, and an entire row is 45 minutes. So, if all the lights are lit up apart from the last 5 then it's about 30mins to high tide. (5 x 6 mins)
In addition, there is an animation that travels up or down the screen, this shows if the tide is coming in/up or going out/down.