Super Mario Bros. X (SMBX) Custom Level - SMBX Custom Level (Boss Rush)
У вашего броузера проблема в совместимости с HTML5
SMBX Custom Level - SMBX Custom Level (Boss Rush) - Created by @Imaynotbehere4long
This level has been played on the old version (1.2) so changes are there on the newer version of this level.
Forum Topic Link: http://www.supermariobrosx.org/forums/viewtopic.php?f=81&t=8890