POWER OF ATTORNEY

      Know all by these presents, that the undersigned hereby constitutes and
appoints each of Chris W. Trester and Yujin Yi of Gibson, Dunn & Crutcher LLP,
with full power of substitution, the undersigned's true and lawful
attorney-in-fact to:

      1.  prepare, execute in the undersigned's name and on the undersigned's
behalf, and submit to the U.S. Securities and Exchange Commission (the "SEC"), a
Form ID, including amendments thereto, and any other documents necessary or
appropriate to obtain codes and passwords enabling the undersigned to make
electronic filings with the SEC of reports required by the Securities Exchange
Act of 1934 or any rule or regulation of the SEC;

      2.  do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to complete and execute such Form ID and
file such form with the SEC and any stock exchange or similar authority; and

      3.  execute for and on behalf of the undersigned, in the undersigned's
capacity as a member, manager, director and/or officer or beneficial owner,
Forms 3, 4, and 5 in accordance with Section 16(a) of the Securities Exchange
Act of 1934 and the rules thereunder;

      4.  do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to complete and execute any such Form 3, 4,
or 5, complete and execute any amendment or amendments thereto, and timely file
such form with the SEC and any securities exchange or similar authority; and

      3.  take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,
in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by such attorney-in-fact on behalf of the
undersigned pursuant to this Power of Attorney shall be in such form and shall
contain such terms and conditions as such attorney-in-fact may approve in such
attorney-in-fact's discretion.

      The undersigned hereby grants to such attorneys in fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney in fact, or such attorney
in fact's substitute or substitutes, shall lawfully do or cause to be done by
virtue of this power of attorney and the rights and powers herein granted.
The undersigned acknowledges that the foregoing attorneys in fact, in serving in
such capacity at the request of the undersigned, are not assuming, any of the
undersigned's responsibilities to comply with the Securities Exchange Act of
1934 or any rule or regulation of the SEC.

      This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to (a) file a Form ID, or any amendments or
changes thereto, with respect to the undersigned's holdings of and transactions
in securities issued by the undersigned, (b) the undersigned is no longer
required to file Forms 3, 4, and 5 with respect to the undersigned's holdings or
(c) revocation by the undersigned in a signed writing delivered to the foregoing
attorneys-in-fact.



      IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 23rd day of October, 2020.



                                             /s/ Tomas Kiselak
                                             ----------------------------------
                                             Tomas Kiselak, an Individual