A complete round includes 5 stages. The stages occur in the following order: green, blue, purple, orange, and bonus. Before the first round of stages starts, the player will be presented with an red introductory stage.
You will only ever play through the red introductory stage once before the first full round of stages begins. It is designed to ease you in to the game. Only one black hole spawns no more than two Uniras at a time (although in the Vs. and FDS versions of the game, this black hole is absent). Bubbles moves particularly slowly, making it very easy to guide Bubbles through the stage.
After completing the first introductory stage, or any of the bonus stages, you begin a new round of stages on the green stage. This stage has a very simple arrangement, with no major features, and two black holes. The golden ingot arrangement on this stage is usually a picture.
Note: In the Vs. or FDS version, an extra bonus stage with a 240 timer count is presented after the very first green stage.
This stage is only slightly more elaborate than the previous green stage, featuring a squeezed in middle section, but otherwise no different. Like the green stage, the golden ingots are usually arranged in a picture, but barriers are more likely to be present.
This is the first stage that features openings on either side of the stage. These openings are found at the top and bottom of the stage, and Bubbles can freely swim through either one and appear on the other side. Uniras are not likely to follow unless pushed through while stunned. The purple stage also features four black holes and a narrowed pathway through the center of the stage. The golden ingot arrangement on this stage is usually a pattern.
This stage is typically the most difficult stage, despite the wide openings on the sides. There are usually a great number of barriers hidden throughout the stage, and they typically block the vertical paths that do not contain black holes. This usually forces Bubbles to travel to the very edge of the screen to traverse between the top and bottom halves of the screen. The wide openings also provide fewer opportunities to smash stunned Uniras. Use caution on this stage and plan your moves carefully. The golden ingots are always arranged in a pattern on this stage.
After completing the difficult orange stage, you are treated to a breather and a chance to earn bonus points. On this stage you race against the timer to uncover special silver ingots, which can be found between each and every peg. The clock counts down from 200. There are a total of 66 ingots, each worth 100 points, with a special 3000 point bonus for uncovering all of them before time runs out.
Note: If you're playing the NES version, due to a mistake in the programming, getting a perfect on a Bonus Stage will only award you 30 points