only print the X after you first print a space...
void loop() {
static int i = 0;
static int a = 0; // move cursor to second line "1" and 9 spaces over
//lcd.setCursor(i, a);
//lcd.print("x"); // display seconds elapsed since power-up
//lcd.print(adc_key_in);
lcd_key = read_LCD_buttons(); // read the buttons
switch (lcd_key) { // depending on which button was pushed, we perform an action
case btnRIGHT: {
lcd.print(" ");
lcd.setCursor(i++, a);
lcd.print("x");
break;
}
case btnLEFT: {
lcd.print(" ");
lcd.setCursor(i--, a);
lcd.print("x");
break;
}
case btnUP: {
lcd.print(" ");
lcd.setCursor(i, a++);
lcd.print("x");
break;
}
case btnDOWN: {
lcd.print(" ");
lcd.setCursor(i, a--);
lcd.print("x");
break;
}
}
}