From the Super Mario Wiki
Kremling Krushin was an online Flash game released to promote the Game Boy Color release of Donkey Kong Country. It could be played on the game's official website, which is currently no longer in use by Nintendo.
The game consists of Donkey Kong confronting three Kremling opponents in separate rounds. He occupies the front plane while the Kremlings occupy the back plane. The player has to press the space bar to toss barrels at the Kremlings and use the "N" and "M" keys to move from side to side and avoid bananas thrown by the enemies. Enemies also attempt to sidestep DK's hits, and get progressively quickier with each round. The player has a limited ammunition of barrels per round (12 barrel in the first, 10 in the second, 7 in the third), as well as three chances to get hit. During every round, an on-screen board tallies the remaining barrels, DK's lives, successful hits, missed throws, and the score, which increases by 10 with every successful hit.
The first opponent is Klump, who can be defeated in 3 hits. The second, Kritter, requires 5 hits. King K. Rool, the final opponent, has to receive 7 hits. If DK gets hit three times or runs out of barrels in a round, the game is over.