Walt should recommend the Interstitial ad format for ads to be shown upon loading the next level during game play.
An interstitial is a full-screen ad that shows for a brief moment as the app transitions to a new screen, such as when there’s a page change or game level load. Interstitials take up the entire screen – and user attention – for a moment. After the interstitial is displayed, a close button is provided for removing the ad.
This question is a part of the Check your Knowledge section of the “Ad Formats and Your In-App Ad Strategy” lesson from the “Configure Mobile In-App Ads Using Ad Manager” unit which is part of the Drive Advertising Revenue with Google Ad Manager course.