AceHack is a variant of NetHack, focusing on gameplay very similar (although not quite identical) to vanilla NetHack, and an improved interface. Work on AceHack as a standalone variant stopped in 2012, after it was merged with NitroHack to form NetHack 4. At present, it is still in an unfinished alpha status, but is nonetheless playable.
AceHack's codebase is mostly based on that of NetHack 3.4.3, but also contains code from UnNetHack (which in turn contains several changes that originally came from AceHack), SLASH'EM, and GruntHack, as well as versions of several patches (often rewritten ones).
The few gameplay changes in AceHack (other than straightforward bug fixes, which tend to change gameplay when they fix exploits) are mostly designed to compensate for the removal of interface drawbacks, to reduce the chance of unavoidable bad luck, or to permit a simpler equivalent to what would otherwise be degenerate strategies, and err on the side of making the game easier:
- Spellbooks can be read even before your memory of the spell wears out.
- The vibrating square is visible from a distance.
- Several items that can be trivially identified now self-identify, such as jumping boots (when worn), scrolls of identify (when picked up in a shop), and potions of oil (at the start of the game).
- Floating eyes, rather than paralyzing a player who attempts to melee them, instead use a gaze that forces players to miss. (They still have their normal effect on monsters.)
- Stormbringer gives the aggravate monster extrinsic, rather than confirming attacks on peaceful and tame monsters.
- Amnesia no longer causes any information to be forgotten that could be remembered simply via keeping notes, instead giving gameplay effects such as removing spells and skills, and causing items to become informally rather than formally identified.
- Swapping your wielded and readied weapons no longer costs a turn. (Readying a weapon directly, something not possible in vanilla NetHack but possible in AceHack, does.)
- Dropping a container on an altar identifies the beatitude of its contents, if it would identify the beatitude of the container itself. (In a related change, unBCUed items now stack with BCUed items that they would otherwise stack with, so there is no incentive to deliberately refuse to learn the beatitude of an item.)
- You cannot destroy a bag of holding by placing a bag of tricks or wand of cancellation in it; doing so will drain all charges from the latter item instead. You can destroy bags of holding by nesting them, but will get a confirmation first.
- Candles are a lot more likely to be generated in the Gnomish Mines, typically in the inventory of gnomes (who will actually use the candles). This is to make it very unlikely that the game will have insufficient randomly-generated candles to perform the Invocation.
- The scroll of charging identifies the number of charges remaining on an object (in addition to its usual effects; this is also still an effect of the scroll of identify). The same effects (charging and identification) also reveal the number of remaining turns that a light source will continue to provide light.
- The weights of inventory items are now visible, whenever the player would be able to touch them to check their weight. (Thus, cockatrice corpses and gray stones do not have visible weights outside the player's inventory.)
Additionally, the monster AI has been improved, particularly for pets. There were some unintentional balance changes as a side-effect of this, particularly for pacifists; the author intends to fix these before release.
One highly notable change is that Elbereth no longer has any special effect; however, its effect is still available in AceHack, as the heptagram, which is identical to an engraved Elbereth, except that it's a symbol rather than a word, and does not exercise Wisdom. It can most simply be dust-engraved by pressing ..
- The illiterate conduct has been split into "no reading or writing of text" (still called "illiterate") and "no writing of heptagrams" ("heptagramless").
- A new "solo mode" prevents bones files from being loaded, and makes startscumming visible (normally, AceHack allows players to view and reroll their stats and inventory before starting the game).
- Game score follows an entirely different algorithm, designed to make scorebearing items like gems and zorkmids have a significant effect on scoring, as well as several other categories (such as experience level), and to penalise spending excessive lengths of time trying to grind up a few more points. It also emphasizes scoring well in every scoring category rather than focusing on just one.
Several more game modes are intended to be added to AceHack eventually (such as Adeon's "Heaven or Hell" variant); there is also a multiplayer version of AceHack under development (intended to eventually be merged with the main codebase), but it is not yet playable. There is also a plan to track more conducts than at present.
AceHack has a philosophy of eliminating options that players will rarely want to change from the defaults, and making sure that the defaults for options are sane. There are typically fewer than ten options that can be changed from within the game, although the list of which options are available tends to change based on player feedback; options are kept only if there is widespread disagreement about what their default value should be (such as floorcolor), if they are needed for compatibility with certain types of terminal (such as color or DECgraphics), or if their setting may need to be changed within a game (such as the pickup_types).
AceHack's most radical changes are in its interface; most obviously, it makes much greater use of color than vanilla NetHack, to allow the player to determine facts about monsters and squares more easily without having to farlook. (For instance, background color is used to distinguish tame, peaceful and hostile monsters, and to show which squares have stairs under items.)
The game's command system has also been redone (although most vanilla commands, apart from rarely-used ones like G and v, still work); the intent is to reduce the number of keystrokes required to type commands, and reduce the risk involved in typing on a laggy connection. The game also tries to detect some inherently dangerous actions (like walking into lava or meleeing a peaceful shopkeeper), and instead of displaying a yes/no prompt (which can easily be triggered by accident when using y to move), requires a prefix; for instance, mk (or m8) would be needed to deliberately move north into lava. (AceHack's default keybindings are a hybrid between the numpad and vi-keys control systems, with either working to move, and # being used for command repeat as well as for extended commands.) There are also several convenience features such as opening doors merely by walking into them, and autoexplore.
AceHack also contains a tutorial mode that teaches players the basics of the commands and gameplay. (It has since been copied by UnNetHack.)
AceHack has several internal changes from NetHack; the main user-visible effects of this are a main menu which allows anyone to enter explore mode and (except on public servers) debug mode, and a different (and hopefully easier to use) build system.