The levels are inhabited by familiar enemies from the Mario universe, including Goombas, Koopa Troopas, Cheep Cheeps, and many others. When these creatures attack Mario, he will lose his current power-up or shrink down to a smaller size if he hasn't already, resulting in him losing a life and having to restart the level.
Mario can regain his normal size by collecting a mushroom, while other power-ups like the Tanooki suit and Flower Suit provide additional abilities to aid him on his journey. The Tanooki suit allows Mario to hover in mid-air while jumping and unleash a spinning attack, making it easier for him to overcome obstacles.