I remember playing AD&D 2e about 20 years ago, and the party was in a dungeon. Long corridor. The wizard type fireballed this enemy that was at the end of the hallway. I asked them to confirm, reminding them it was in a confined area. "Oh yeah, I totally do it." The other players nod in agreement.
I say, "All right, roll for damage," and pull out a calculator. 33000 cubic feet, divided by 10 feet wide x 10 feet high = 330 feet of corridor filled. I measured the space all around, figuring that it would expand equally in both directions, but then would back fill in the other direction if it filled the space one way. The players are baffled as I shuffle between the calculator and the GM map, counting squares.
I state: "Okay, the fireball explodes in bright fire, and the expanding flames blast toward you, covering you and the 130 feet of corridor behind you in the explosion. If you make your saving throws, its half damage."
The players are all indiginent, "What, the spell doesn't work that way!?" I pull out the PHB and read to them the spell description, emphasizing the important bits.
"The caster fires a streak from their finger out to the range they desire, and if the path is unobstructed, the spell creates an explosive burst of flame that detonates with a low roar at that point. If the streak strikes something before it reaches that range, it detonates early It deals 1d6 damage per caster level to creatures in the area (creatures affected can save for half damage). There is not much pressure with the explosion, and it will conform to the shape of the area it bursts in, covering an area equal to its normal spherical volume (roughly 33,000 cubic feet). The fireball ignites combustibles, and melts soft metals such as gold, silver, and copper. Items exposed to the fire must make saves to negate the effect."
Splutter, splutter. "Well, we never played that way."
I responded. "I'm not responsible for your house rules."