Damn I thought I had actually invented a new single player mini-game in Minecraft, that is, until I checked the web and found some Youtube videos of people doing it (kinda, sort of). I still thought the idea was worth sharing in case, like me, you had never heard of it before now.
There is a game in Minecraft called Spleef where two or four players “fight” in an arena on a floor made of one layer of wool (or snow, etc.) blocks. There is almost always a long drop, a mob trap, or lava beneath the floor (i.e. death). The object is to break the blocks around and hopefully under the other player(s) by various methods and make them fall. The game is fun because it involves a lot of frantic running around and parkour style jumping while trying to avoid being trapped by gaps too wide to jump.
I was doing some landscape alteration around my portal blockhouse in the Nether (hell) to get rid of the big lava flows and pools because I’m tired of killing Ghasts only to see the tear and experience they drop fall into the lava. While I was doing this I suddenly got an idea, what if I built a single layer thick platform out of “netherrack” (easily breakable Nether stone) out over a lava lake and then fought Ghasts from it? That way I could play Spleef (of sorts) any time I wanted to in single player if I was bored and wanted to get the adrenaline going.
The result was a 40 by 40 block single layer platform of netherrack ringed by a one block high raised smooth stone (impervious to ghast fire charges) rim. I also built a tiny stone blockhouse sticking outwards from the center of one side so that I could spawn the Ghasts while hiding inside until they got airborne. To keep it challenging I wear non-enchanted iron armor and use no fire resistance or other potions.
To start the game simply go into creative mode and give yourself some (how many depends on your skill) Ghast spawn eggs, then go back to normal mode before throwing them out into the platform area. Wait a few seconds inside the blockhouse for the Ghasts to get properly airborne and then charge out and start fighting for your life. Every time a Ghast shoots a fire charge at you and misses it blows at least a 3x3 hole in the platform while also setting a couple of the surrounding blocks on fire.
Ghasts only take a couple of arrow or sword hits to kill and are generally considered to be only moderately difficult to fight. But when you are trapped on a confined and rapidly disappearing platform and there are four of them floating around shooting fire charges at you it is a very different story. The bow is obviously your main weapon since Ghasts very rarely come down into sword range but when drawing the bow you can only move at a crawl and can do almost nothing to dodge incoming attacks.
After trying this a few times and finding it to be a very satisfactory means to get myself cursing at my monitor while experiencing elevated blood pressure and heart rate I really thought I was on to something. Of course it turned out that other people have had more or less the same idea already. In hindsight I admit that it is a fairly obvious way to use Ghasts as an opponent in the single player game. Still, even if I cannot take any credit for it I recommend Minecraft players trying this out if you really want an extreme challenge that will get your heart going.
The platform should be completely over a large lava lake in a high ceilinged area that is clear of aerial obstructions (not very hard to find in the Nether). To adjust the difficulty you can make the platform larger or smaller and of course also vary the number of Ghasts you spawn in. Also note that if you build the platform too high above the lava lake the Ghasts will often drop below the platform, lose line of sight, and stop firing while still being sitting ducks for your arrows fired down from the edge. To keep the game challenging I recommend building the platform only four or five blocks above the lava so that the Ghasts are always in line of sight with you.
Have fun and please try to not swim in the lava too much… :p