update method

void update()

Updates the position and content of the column.

Moves the column down by speed. If it goes off-screen, it resets to the top. Also randomly changes some characters to create the "glitch" effect.

Implementation

void update() {
  y += speed;

  if (y > screenHeight) {
    y = -length * 15.0;
    _generateCharacters();
  }

  if (_random.nextDouble() > 0.9) {
    int index = _random.nextInt(length);
    characters[index] = chars[_random.nextInt(chars.length)];
  }
}