EXHIBIT 99.1

AGREEMENT REGARDING JOINT FILING

OF STATEMENT ON SCHEDULE 13D OR 13G

The undersigned agree to file jointly with the Securities and Exchange Commission (the “SEC”) any and all statements on Schedule 13D or Schedule 13G and Forms 3, 4 and 5 (and any amendments or supplements thereto) required under section 13(d) or section 16(a) of the Securities Exchange Act of 1934, as amended, in connection with purchases and sales by the undersigned of securities of any issuer, until such time as the undersigned file with the SEC a statement terminating this Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G. For that purpose, the undersigned hereby constitute and appoint Darlington Partners Capital Management, LP, a Delaware limited partnership, as their true and lawful agent and attorney-in-fact, with full power and authority for and on behalf of the undersigned to prepare or cause to be prepared, sign, file with the SEC and furnish to any other person all certificates, instruments, agreements and documents necessary to comply with section 13(d) and section 16(a) of the Securities Exchange Act of 1934, as amended, in connection with said purchases and sales, and to do and perform every act necessary and proper to be done incident to the exercise of the foregoing power, as fully as the undersigned might or could do if personally present, until such time as the undersigned file with the SEC a statement terminating this Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G.

Dated: April 12, 2021

DARLINGTON PARTNERS CAPITAL MANAGEMENT, LP

By: Darlington Partners GP, LLC,
General Partner

By: /s/ Scott W. Clark
Scott W. Clark, Manager

DARLINGTON PARTNERS GP, LLC

By: /s/ Scott W. Clark
Scott W. Clark, Manager

/s/ Scott W. Clark
Scott W. Clark

/s/ Ramsey B. Jishi
Ramsey B. Jishi

DARLINGTON PARTNERS, L.P.

By: Darlington Partners GP, LLC,

By: /s/ Scott W. Clark
Scott W. Clark, Manager

Six Flags Entertainment Corporation/NEW SCHEDULE 13G/A