qmk-firmware/quantum/led_matrix/animations/band_spiral_anim.h

#ifdef ENABLE_LED_MATRIX_BAND_SPIRAL
LED_MATRIX_EFFECT(BAND_SPIRAL)
#    ifdef LED_MATRIX_CUSTOM_EFFECT_IMPLS

static uint8_t BAND_SPIRAL_math(uint8_t val, int16_t dx, int16_t dy, uint8_t dist, uint8_t time) {
    return scale8(val + dist - time - atan2_8(dy, dx), val);
}

bool BAND_SPIRAL(effect_params_t* params) {
    return effect_runner_dx_dy_dist(params, &BAND_SPIRAL_math);
}

#    endif // LED_MATRIX_CUSTOM_EFFECT_IMPLS
#endif     // ENABLE_LED_MATRIX_BAND_SPIRAL