Leds not bright

hey guys... im starting with arduino and i hope you get this question easy to answer
sory for the bad english but im an argentinian

so i was trying to combine two simple codes just for fun..
one is the potenciometer code with one led
and the other one is the ping pong code of leds
so the potenciometer configurates the velocity of the ping pong

and its running properly(i think so) the only problem i have is that the leds blink is soft(i dont know if its that word) or dim

is like they dont have power enough, the connections are fine but i think my problem is in the code

int sensorPin = A0; // The potentiometer is connected to analog pin 0
int ledPins[] = {10,11,12,13}; // The LED is connected to digital pin 10 11 12 13
int sensorValue; //We declare another integer variable to store the value of the potentiometer
int index;

void setup() // this function runs once when the sketch starts up
{

pinMode(ledPins[10],OUTPUT); // ledPins[10] = 0
pinMode(ledPins[11],OUTPUT); // ledPins[11] = 1
pinMode(ledPins[12],OUTPUT); // ledPins[12] = 2
pinMode(ledPins[13],OUTPUT); // ledPins[13] = 3
}

void loop() // this function runs repeatedly after setup() finishes
{
sensorValue = analogRead(sensorPin);
pingPong();
}
void pingPong()
{

for(index = 0; index <= 3; index = ++index) // step through the LEDs, from 0 to 3
{
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(sensorValue); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}

for(index = 3; index >= 0; index = --index) // step through the LEDs, from 3 to 0
{
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(sensorValue); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
}
hope you can help me i would apreciate so much

What size pot and a schematic of some description would also have been great.

Maybe attach them to your next post

In setup() you need to use indexes 0 to 3 for your ledPins array, not 10,11,12,13.

change the indexes as the previous comment says.
In addition to that, Try not using the pin 13 because it's already used by an on-board LED.
To check if you have problems with hardware:
What resistor value do you use for each LED ?

Just like the above post, what type of resistor value do you use.

Try using a lesser value if you have them.

Just try not to go under 220 ohms for 5v or 100 ohms for 3.3v or you will likely fry them.

I already fried 3 LEDs because I forgot to put a resistor in. :frowning: