The most immediate bit of unusual design is that the game is played in portrait mode, rather than landscape. Also, instead of gaining levels, characters randomly get a level-up equivalent stat boost after battles (and I found them very frequent, even in battles against weaker enemies). The “numbers” of this game are very tightly designed; once you get the next set of equipment in any area, the monsters in the previous area are suddenly doing only 1 damage to you and you're killing them in one hit. But that's only with equipment—leveling gains are very gradual. There are three difficulty levels, and you can switch between them at any time.
The magic system is very simple: Each character has one unique spell, and then can equip elemental gems in various combinations to get the other 11, which are a mix of attack, healing and status effects. Elemental weaknesses and buffs/debuffs don't really exist. (There appear to be two fulls sets of gems in the main game, one in the post-game, and one in the post-post-game.) The other noteworthy system in the game is “Potential Bits”, which you acquire slowly from defeating bosses, but can be set for various passive special abilities, like regeneration or half damage from physical attacks. The one that allows rare drops makes most enemies drop stat-increasing seeds.
The dungeons are pretty much all straight lines with short treasure branches; and it's generally required to follow those branches given the major effect equipment has on your characters' effectiveness. They do try to manage a few puzzles, including several areas where you need to use consumables periodically to get through and a brief segment of math word problems. The post-game includes several optional dungeons that are actual mazes.
The big plot twist (which I saw coming well in advance, as should anyone familiar with Phantasy Star 3) is that the characters are not on Earth, but instead in a biosphere dome on Mars. And the computer system that maintains it is breaking down. This actually works well with the relatively tiny world the game inhabits: Of course there are only a handful of settlements a few minutes away from each other; there's only so much space inside a dome!
And to be fair, I like this sort of plotline, where the science that built the world has degenerated into fragmented myths. And though the translation limits it a bit, I like the inclusion of hard choices like disabling the “Mother” machine (and thereby dooming the El) to revive a automaton that can potentially help repair the whole world.
The game is super-short: You can reach the credits-roll ending in about three hours. The post-game, aka “Chapter 2,” picks up a year later and lets you access several new areas along with unlocking the blue chests scattered throughout the game (each contains one Potential Bit). This leads to a second final boss and an additional ending; and you can get there in another two hours or less. Then there's the post-post-game, where you can randomly access a series of bonus dungeons and areas where the ultimate weapons are kept and fight an even more final-er bonus boss.
Overall: Very short, relatively easy, a little clunky but some interesting ideas, and it stands out from the usual Exe-Create/KEMCO games in a bunch of ways. And I couldn't argue with the price.