the fundamental genius of the kururin trilogy derives from its unique, bare bones approach to the technique of constantly altering outcomes over time. consider a racing game: part of the appeal of the genre is how the timing of every action will alter the outcome of each action that comes after it. taking a turn not only changes your speed and direction in the moment, but it will also affect the speed at which you arrive at the next turn, which will affect the requisite braking power needed for said turn, the best line to take through the curve, and potentially the performance of your vehicle assuming that you're playing with something where the powerband or other handling element of the vehicle matters. varying when and/or how you take the turn adds nuance to the way you must approach each section afterwards. it is easy to call a racing game a "puzzle" of sorts because one could effectively "solve" the right actions to do at each point in the track, but with an incredibly dense state space that inhibits reproducibility (aka requiring precision to recreate particular states that most players won't be able to perform consistently) and a model that alters behavior based on previous actions, the game can let the player get the gist on how to handle a turn while forcing them to continue paying constant attention to their car's state and reacting to handling nuances that they may not have explicitly encountered before.

the kururin series does this without the dense state space by instead keeping the character's long, stick-like ship constantly turning while punishing contact with any obstacles. the player tracks very little but the rotation of the ship and the location of various moving obstacles, yet small variations in timing will change the phase of the ship's rotation for future movement and thus force a reevaluation on how to move through future corridors. in some ways the unforgiving, ticky-tacky movement (the player has three discrete speeds to choose from) actually enhances this effect by in its own way inhibiting reproducibility; racing games require subtle input shifts to provide handling differences, but the comparative obviousness (and slow rotation speed) of kururin's gimmick more or less necessitates large, unsubtle movement inputs to actually yield new effects down the line.

however, because of the cyclical nature of the helirin's (the ship's) rotation, desired states will always reoccur provided the player has space to sit and wait, giving a start-and-stop effect to play that can become underwhelming. this kills the above effect as well, as the ability to frequently reset your state ignores the gradual changes in outcome that makes the above playstyle so compelling. the first game suffered immensely from this issue in its larger stages thanks to obstacles with their own cycles requiring a synchronization between the helirin and the obstacle that could potentially take multiple rotations to occur based on the difference in period between the two. it attempted to solve this by allowing you to change your rotation phase via springs that bounce you in the other direction, which were often stacked in such a way you could create a holding pattern for the helirin until achieving a desired phase and proceeding through the obstacle. still, this is just a spin on waiting in place. paradise smartly fixes this by finally giving the player control over their rotation speed. even with only a single speed increase to work with, the player has significantly more leverage on how to deal with moving obstacles, and the designers can in turn decrease the amount of reset points from levels, resulting in a more compact and intense scenario feel overall.

indeed, as the first game devolved into gauntlets of obstacles that rewarded consistency over analysis of the interactions that arise from the rotation, paradise goes in the other direction. the clock level... oh my god, what a mind-fuck moment when I first played this game years and years ago. a clock-face maze with two giant rotating arms (one clockwise, one counter-clockwise) forms the majority of this level, bookended by two small obstacle generator sections. the clock face is deceptively open, but one quickly finds that the incursion of the arms prevents one from staying in place, and the design of the different corridors within the clock face make it necessary to switch between clockwise and counter-clockwise in order to move through it, especially if one wishes to get the key rising on the top side of the structure. later levels experiment with other gimmicks, such as ghosts that jump onto the ship and slow it down, forcing the player to move into higher speeds through tight areas and then instantly switch out as soon as the ghosts leave, and sliding walls that change the layout of the level as it progresses, disorienting the player as they progress to the exit. other levels also retain the open routing of the clock level far more than the game's on-rails predecessor, often by creating seemingly random wall structures that offer multiple different routes with escalating difficulty depending on where one finds little crevices to sneak through between surfaces. this is iterated upon with extra areas unlocked with keys on a surprising amount of levels, often with the keys themselves residing in out-of-the-way sections of other levels. all in all, it's quite the leap over the original kururin in confidence of design, even as the true final level begins to recede into the same tiring gauntlets as the original.

what will be somewhat more polarizing to a new player are the minigames. the titular hero must rescue his family members from a circus troupe (I think?), each of whom provides a minigame as prerequisite for freeing one of the prisoners. in the best cases, this involves a twist upon the core mechanics of the game, such as changing the length of the helirin over time or having it carry items that jut out from its arms. a particular lawnmower game provides a rather interesting test in how to actually cover area with the helirin as opposed just to avoiding contact. others are perfunctory (the flappy bird minigame early on) or downright unpleasant (the strict and unwieldy racing game). a particular minigame requires you to rotate the screen on its side to get a vertical view of the helirin tumbling down a rock shaft collecting some items or whatever. begs the question of why we don't have a screen rotation mode in mgba yet? perhaps there's not enough other gba games that use this gimmick; I imagine that the advent of the clamshell GBA SP basically nixed that idea for any future titles.