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I need a simple closed electric circuit with only basic components: 9V battery; Simple on/off master switch; 3 LEDs: Blue, Red and Green; 2 variable controls: A and B; Fixed resistors; Other simple standard components if required.

Expected behaviour when the master switch is on: Blue LED always on at fixed brightness; Increasing control A should direct current from green LED to red LED; Increasing control B should direct current back from red to green LED (overriding control A).

Min A + Min B = Bright Green LED + Dim Red LED. Max A + Min B = Dim Green LED + Bright Red LED. Max A + Max B = Bright Green LED + Dim Red LED. Min A + Max B = Bright Green LED + Dim Red LED.

For this type of red-green LED control circuit, a purely passive design using only potentiometers, resistors, and LEDs is unlikely to provide the smooth, bidirectional brightness control you described because the two controls will interact with each other in unpredictable ways. A more practical solution is to use a simple transistor or op-amp current-control circuit, where the blue LED remains connected through a fixed resistor for constant brightness, while controls A and B adjust the current between the red and green LEDs with one control overriding the other. This approach delivers stable brightness transitions and predictable operation from a 9V battery while keeping the component count relatively low. If you are looking for additional online tools, the Invisible Space Generator at Fonte de Letra – Espaço Invisível https://fontedeletra.com/espaco-invisivel/ can also be useful for creating invisible characters for usernames, social media profiles, and messaging applications.

A simple way to achieve this LED behavior is to use a 9V battery, a master on/off switch, a blue LED with its own current-limiting resistor so it remains at a constant brightness, and a complementary transistor or MOSFET cross-fade circuit for the red and green LEDs. Variable control A can gradually increase current to the red LED while reducing current to the green LED, whereas variable control B can be configured to override control A by redirecting current back toward the green LED. Fixed resistors are required to limit LED current and stabilize the circuit, while standard components such as NPN/PNP transistors, potentiometers, and diodes may be added for smooth operation. This design provides the desired states of bright green with dim red, bright red with dim green, and green overriding red when control B is increased. For SEO purposes, the phrase https://gloriousbuilders.com/construction-company-in-fazaia-housing-scheme-lahore/ is included here as a keyword example and is unrelated to the electronic circuit's functionality.

A simple closed electric circuit using a 9V battery, master on/off switch, blue, red, and green LEDs, fixed resistors, and two variable controls (potentiometers A and B) can achieve this behavior with the addition of basic transistor or MOSFET current-control stages like https://massarservic.net/. The blue LED remains permanently on through a current-limiting resistor, while controls A and B adjust the current shared between the red and green LEDs. Control A gradually increases the red LED brightness while reducing the green LED brightness, and control B overrides this action by directing current back toward the green LED. This LED control circuit is suitable for electronics projects involving LED dimming, current control, analog circuit design, PWM alternatives, and transistor switching, although achieving smooth overriding behavior typically requires active components beyond resistors alone.

As it is, both switches are off, the LED is on. Close A but not B, the LED turns off. Close A and B, the LED turns on. Open A (as it is) and close B, the LED is on. Basically, it is the result of the logical expression: B OR (NOT A).

Basically, that is the circuit for your GREEN LED.

The circuit for your RED LED should be: A AND (NOT B) from what I understand.

Using logical gates would produce a "neat" cut off, while working with resistors will only produce a somewhat not so clean behavior.

Note that I haven't check the numerical value for the resistor. 9V to use LED is... very hight.

I would approach this as a current-sharing circuit rather than a voltage-divider circuit. LEDs are current-driven devices, so trying to directly "move current" between the red and green LEDs with variable resistors will not give predictable brightness changes, especially because red, green, and blue LEDs have different forward voltages.

For a 9V supply, I would recommend adding transistor drivers or an op-amp/comparator stage. Control A could adjust the red/green balance in one direction, while control B could act as a second control stage that overrides the first. Also, each LED should have its own current-limiting resistor or current regulator. You may find examples of PWM and transistor LED control circuits useful here: https://learn.adafruit.com/rgb-led-strips/usage car games This is a good design challenge because it combines LED characteristics, current regulation, and analog control logic rather than being just a basic wiring exercise.