I recently played through a short game released on the Sega Genesis many years ago called Beyond Oasis using my Wii's Virtual Console. I never owned a Genesis, so I never knew anything about this game until I played it. It really isn't a bad game at all. It is a nice action/adventure/RPG hybrid with well-designed puzzles, a fun combat system, and solid execution. If the game was a little longer, a lot less linear, and had better music, it might have been able to stand as an equal to the Legend of Zelda series.
One of the most important aspects of Beyond Oasis is its spirit summoning system, which is central to almost all of the puzzles and tactics in the game. Basically, as you progress through the game you acquire four spirits who you can summon using the "Light Ball" released from the hero's magical Gold Armlet. If the Light Ball strikes water you will summon the water spirit, if it strikes fire you will summon the fire spirit, etc. The game designers were pretty impressively thorough with this, too. You can summon the water spirit by hitting a slime monster with the Light Ball or even summon the fire spirit by hitting an enemy mage's flame shot. There are even a few odd ways to summon a spirit like hitting the elder of a town with the Light Ball to earn the shadow spirit (it doesn't work when I hit other humans, so I am still trying to figure out the logic), so the game rewards experimentation and creativity. There are many places where creative choices on when to summon which spirit are necessary to solve the puzzles. As a whole, this system works very well, and my only complaint is that there are far too few ways to summon the plant spirit compared to the others (it seems odd that I can't summon the plant spirit by hitting grass or trees when the others are far less restrictive).
Another thing I find interesting about the spirit system is that the spirits are both under your control and somewhat autonomous. Once summoned, the spirits can move around on their own (though usually sticking close to the hero) and can attack on their own, though the degree to which they do this varies widely depending on the spirit. At the same time, you can order the spirits to cast various spells that they will unleash from their position. This semi-autonomous nature can be both good and bad. Certainly, it makes quick and precise aiming of magical effects like the Water Bubble or Fire Breath almost impossible, to the point that I needed to use an expensive wide area explosion spell to light torches, but at the same time the automatic attacks from the fire spirit are strong, quick, and accurate and don't require any of the player's attention. All of the plant and shadow spirit moves work well (since you control their movements precisely, though the plant spirit attacks on its own), but only the water spirit's healing move (which thankfully automatically seeks out the hero) and the fire spirit's big explosion and automatic attacks are reliable under normal conditions. The frustrating fire spirit racing minigame is one place in particular where I desperately wished for a way to manually control the movements of one of the spirits. Overall, I think the game would have been a bit better if either the designers got rid of the moves that required you to precisely position a spirit that is eager to move around on its own, or enabled the spirits to move themselves into position to attack accurately when ordered.
Anyways, I do like the different focuses they gave each of the spirits. The water spirit heals and stuns enemies, so you use it to recover from injuries, reduce damage, and give yourself an opening to attack with your own weapons. The fire spirit aggressively attacks on its own and is particularly effective against certain enemies (like zombies), so it is great in a tough fight against a swarm of foes, or when you don't have the freedom to attack yourself. The shadow spirit negates hits and catches you when you fall, so you use it when you are at risk of taking a lot of attacks you can't dodge. The plant spirit can utterly destroy every enemy that gets too close to it, so it is great for holding positions and clearing out waves of enemies. Each spirit has it own strategy, either defensive or offensive, and the same battle can be fought in very different ways depending on which spirit you bring to it. This kind of tactical variety is really great, and helps a lot with keeping the battles in Beyond oasis exciting until the end.
There are probably a few more things I could take about regarding the game, like its items (limited inventory encourages use and foresight, but at the same time you just get way more great items than you really need), weapons (limited use weapons work surprisingly well here, other than bows), the rank system (too random and the hearts fade too quickly), and finding jewels (a great consistent and useful puzzle reward), but none of those aspects of the game are unique or notable enough to really get into detail about.
Overall, not a bad game at all. I just wish I knew where those last seventeen jewels were, since I thought I was a lot more thorough than that...