Ideas for a Sudoku puzzle system that could coexist with or replace Sokoban:

• The puzzle part of the level would be represented by an 11x11 grid (9 3x3 areas with 2 rows/columns of some other terrain to separate them).
• The solution must be given by engraving numbers on squares, with certain numbers burnt into the floor. This would require a level flag that provides 2 special cases to engravings: 1) that non-Elbereth engravings do not degrade normally, so you can write numbers in the dust without smudging them; and 2) it is impossible to erase a burnt engraving.
• The solution must be given by dropping rocks of the appropriate quantity onto the squares of the grid to represent each number.
• Both of the above solutions have the issue that the grid is practically unreadable and it basically forces the player to copy the puzzle out of the game, solve it, then copy the solution back in. One solution is to have spaces containing nothing except the requisite solution display as one of a set of 9 new glyphs that display as the number 1-9.
• Another solution is to avoid numbers and use object classes (weapon, armor, scroll, ring, wand, potion, gem, spellbook, and amulet), since there is no particular reason Sudoku has to use the numbers 1-9.
  • This means the puzzle would be solved by having 1 of each object class in each row, column, and sub-grid.
  • The “fixed” objects provided as a starting point could either be immovable, or movable but required to put back in place for the puzzle to be solved (i.e. the puzzle is checking not for any valid Sudoku solution, but a valid Sudoku solution in which the starting objects haven’t moved).
  • The main issue with this suggestion is avoiding providing the player with a bunch of free resources and not requiring them to amass 7-9 of each object class before starting. One way to work around it is to add a new object to each object class that does nothing and never generates outside of the Sudoku level, where exactly 9 of each will appear in every puzzle between the initial ones and the “stock piles”.

If you kick a wall (or stone terrain), there is a small chance that a rock comes loose from the wall and drops at your feet, or sometimes from the ceiling, in which case it hits you on the head.

A drum of earthquake also causes rocks to randomly be shaken loose from the ceiling in their radius of effect and hit any monster that happens to be on their square.

Zapping a wand of locking or casting wizard lock at a pile of rocks will turn it into a wall, or possibly a boulder if creating walls is too powerful.

The “Construction Patch”:

• When digging out stone (not necessarily walls) with a pick, rocks may fall on your head with a lowish chance, about 10% per dug square. These deal the least damage if you are wearing a dwarven helm, and a little less than normal if you are wearing some other hard helm. Dwarvish characters have a high chance of dodging the falling debris entirely. Possibly also allow a boulder falling on your head from digging similar to when monsters tunnel.
• You can apply rocks at an adjacent floor square to build a wall. It takes 50 rocks, or 25 if there is a boulder in that square. (If the space is marked as being wall-nondiggable, this either doesn’t work, or flips the space to being diggable.) It takes 1 turn per rock to build it. In the process it creates an immovable object or dungeon feature called “partially-built wall” on that space, which tracks how many rocks are part of it. If you move onto the space, you can dismantle the wall and retrieve the rocks.
• You can apply rocks at an adjacent pool or moat to attempt to fill it. The more rocks, the higher the chance of filling it. This takes only 1 turn.
• Stone to fleshing diggable wall turns it into huge chunks of meat.
• Force bolts from striking wands or the spell scatter rocks off diggable walls they hit, and in roughly 5 shots the wall is destroyed.
• Digging a pit or hole puts a pile of rocks on a random adjacent square.
• When you dig a hole and fall down to the next level, you are usually accompanied by a shower of rocks falling on and around you. Dwarves are more adept at dodging and getting hit by fewer rocks.
• When using a pick to dig a square of natural stone where the four orthogonally adjacent squares are all dug out already, you are asked if you want to carve out a boulder. If you say yes, a boulder is deposited on the new space.

Note that the two boulder-creation methods above run the risk of being exploited for abusable quantities of food if you have stone to flesh available, and the stone-to-flesh-walls method explicitly invokes this.

A new race whose primary feature is that it eats minerals: gets nutrition mainly from rocks, may be able to eat metals, and gains limited spell-like abilities based on the last precious gem they consumed. A couple non-comprehensive examples:

• Eating a ruby grants the power to cast fireballs.
• Eating a jet stone grants the power to make clouds of darkness.

The abilities could be triggered using #monster, and would probably have a finite pool of uses, after which they can no longer be used. Eating another gem before this pool runs out would swap in new abilities and either give a fresh pool of uses or add to the existing one.

Falling rock traps can dump multiple rocks onto you at once, up to (depth/4). Damage is taken for each rock. If a trap would drop 4 or more rocks on you, it may instead drop (rocks/4) boulders on your head instead. Helms should be less effective at reducing damage from falling rocks, and almost useless at reducing damage from falling houlders.

If multiple boulders are dropped, they might be dropped on nearby spaces as well, so that a pathway might end up blocked.

Snow golems occasionally drop one or more of the following when killed:

• carrot
• fedora or elven helm
• random cloak, possibly slightly eroded, rarely of frost
• random pair of gloves, possibly slightly eroded, rarely of frost
• a few rocks, or possibly jet stones

If you get hit by a cursed rock from a falling rock trap, you may become stunned for a few turns.

You can untrap falling rock traps. Unlike dart and arrow traps, this just dumps all the remaining rocks onto that space all at once with the message “The rocks clatter onto the ground”. If there is a monster on this space, it gets hit repeatedly by each rock.

Zapping a digging ray upward may either detach a boulder from the ceiling, or several rocks, instead of a single rock. If several rocks are released, each gets a separate damage roll.

Whetstones, imported from SLASH’EM, but with some additional effects.

• The behavior from SLASH’EM is that whetstones can be used at a water source to remove rust and negative enchantment from edged weapons and pick-axes.
• Cursed whetstones either weld themselves to your hand or have a chance of breaking a weapon rubbed on them.
• Blessed whetstones can uncurse a cursed weapon rubbed on them, but at the cost of removing the whetstone’s blessing.
• If slingshot is implemented, rubbing rocks on a whetstone will break them into slingshot.

Characters with at least Basic in sling can do something (use a touchstone? flint stone? any gray stone?) to break rocks into slingshot, which weigh 1 and have comparable to-hit and damage to flint stones. Slingshot may be weapon-class instead of rock-class. The higher the sling skill, the more shot that one can get out of a single rock. There should also be rare silver rocks, which can be broken into silver shot.

Air elementals drop some rocks (and “sticks” - the occasional wand of nothing?) which is the debris you have been pummeled with. (Also makes the Plane of Air a little less difficult to cross if you haven’t got a levitation source.)

You can fill a pit by dumping sufficient rocks in it.

The rocks generated by smashing a boulder or statue should never weigh more than the boulder or statue.

You can put rocks into a sack, oilskin sack, or bag of holding and then wield it and swing it at enemies. (This uses flail skill.) Damage depends on the total weight of the rocks.