On the left, gambling and codebreaking screens. The 5-across slot reels give you 3 chances to win: 1-2-3, 2-3-4, or 3-4-5; and the wheels work one of two ways: a spinner stops on a result for you to get that prize (or penalty), or you pick a color and win if you stop the spinner there by hopping on the appropriate switch.
On the right, piece-together pinball platforming segments.
On the left, vertical-oriented elevator/lift paths to mix-and-match.
On the right, other platforming lift/obstacle pathways. Simply eliminate a set number of segments (5 or so); and have them follow whatever remains intact.
Left: Cluster-together procedural pipemazes.
Right: More simple pathway formations.
Left: Some incomplete pushblock room/formations.
Right: Gravity-inversion level design rooms.
Left: Clusters of blocks where a dozen or so can be removed from various coordinate combos while remaining navigable.
Right: Horizontal-oriented and vertical-oriented pathway puzzles/loops.
Not level design per se, but the initial framework for a flexible action spriteset layout. Flipping/rotating and resequencing can make for the most flexible set of actions in a sprite this simple ever (once I actually have time to digitize it!), and by combining this with various blurs (which incidentally define offensive hitboxes, as opposed to the sprite's defensive ones) would make for quite a powerfully creative combo.