qmk_firmware/quantum/rgb_matrix_animations/solid_reactive_simple_anim.h

#ifdef RGB_MATRIX_KEYREACTIVE_ENABLED
#    ifndef DISABLE_RGB_MATRIX_SOLID_REACTIVE_SIMPLE
RGB_MATRIX_EFFECT(SOLID_REACTIVE_SIMPLE)
#        ifdef RGB_MATRIX_CUSTOM_EFFECT_IMPLS

static HSV SOLID_REACTIVE_SIMPLE_math(HSV hsv, uint16_t offset) {
    hsv.v = scale8(255 - offset, hsv.v);
    return hsv;
}

bool SOLID_REACTIVE_SIMPLE(effect_params_t* params) { return effect_runner_reactive(params, &SOLID_REACTIVE_SIMPLE_math); }

#        endif  // RGB_MATRIX_CUSTOM_EFFECT_IMPLS
#    endif      // DISABLE_RGB_MATRIX_SOLID_REACTIVE_SIMPLE
#endif          // RGB_MATRIX_KEYREACTIVE_ENABLED