How to delay a LED?? (On/Off)

I need to at least delay my LED. I'm ONLY allowed to use BJT and resistors. ( No Diode, Relay, Capacitors and IC's etc.)

Details: there are 7 LEDS in total.

There are 7 levels in the container which the led's indicate.

If the container is "empty" the 1st led is "on".

If the water reaches to the 2nd led/level, "on" and the 1st led will turn off.

3rd led/level = On ; 2nd and 1st = Off

4th led/level = On ; 3rd, 2nd, 1st = Off

5th led/level = On ; 4,3,2,1 = Off

6th led/level = On ; 5,4,3,2,1 = Off

If the water reaches to 7th led/level all led's is "Off" but after a delay in (secs, milliseconds) all the leds will turned "On"

I need any kind of help or advice to do this project. thankyouu!

by amsnklmf
March 13, 2019

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