Ernesto, like Fidel, is a turn-based dungeon crawler that allows for unlimited rewinding so long as the player has any health remaining. It's a much shorter game with a minimal four-level structure:

1. four entrance/exit points, no bosses
   
2. two entrance/exit points, one Golem
   
3. two entrance/exit points, one Golem
   
4. one entrance, one exit, three Dungeon Gods

The only requirement for beating Ernesto is to slay all three Dungeon Gods with at least one health point remaining. Points are then awarded equal to the amount of treasure collected. Treasure has no use during gameplay and is used only as a scorekeeping mechanism.

To start Ernesto,you must have beaten the first playthrough of Fidel and have gained access to the nightmare realm. From the menu screen, head north toward the nightmare portal. Bark at each of the two torches along the bridge. Once both torches are extinguished, the portal will close and a voodoo doll will be revealed. Step onto the voodoo doll to launch Ernesto.

The screen for Ernesto has two zones: the dungeon grid and the status bar.

The dungeon is a 10×7 grid. In levels 1–3, all spaces are filled with a semi-random array of treasure, enemies, weapons, and other entities. Ernesto can visit each of these grid spaces a single time by moving north, south, east and west one square at a time. Ernesto leaves a trail behind him and cannot cross his trail. Some number of entrance/exit points are generated where Ernesto can start and end his trek across the dungeon.

Level 4 uses only a small portion of the possible dungeon grid and has a set configuration. It has one entrance point and one exit point, and the two are not interchangeable.

The status bar includes information about Ernesto's current health and abilities. It also gives information about the dungeon grid.

Avatar
Ernesto appears to be healthy, critically injured, or poisoned. If Ernesto is both critically injured and poisoned, he will appear to be critically injured.

Health meter
The health meter starts with 2 bars and gradually grows as Ernesto becomes stronger. A red bar represents a health point. An black bar represents potential health point that can be earned with a med kit. A black bar outlined with green represents a potential health point that can't be earned until Ernesto is cured of poisoning.

Experience meter
The experience meter starts empty and fills as Ernesto has successful confrontations with enemies. Each time the experience meter reaches capacity, Ernesto's attack power increases by 1 and the meter is reset. (After Ernesto's attack power reaches 3, his attack power does not always increase when the meter reaches capacity.)

Weapon
Ernesto begins with a whip and at any time can pick-up either of two weapons found in the dungeon. Ernesto can hold only one weapon at a time, so he loses his previous weapon every time he acquires a new one. Weapon-type affects only bosses.

Attack power
Ernesto's attack power indicates how much damage he can deal an enemy upon an encounter. His initial attack power of 1 allows him to kill only bats. After two successful bat kills, Ernest will gain enough experience points to increase his attack power to 2 which will allow him to kill snakes and fanatics.

Wealth
Ernesto's final score is measured by the treasures he finds along the way. Treasures have no use during the game.

Descriptor
Hovering the cursor over a dungeon tile will call up information about the tile's contents.

Each of the first three levels of Ernesto is a procedurally generated grid containing the following tiles:

• treasures, which have no use during gameplay but are worth points upon victory
  
  • coins (worth 1 point upon victory)
    
  • emeralds (worth 2 points upon victory)
    
  • chests (worth 4 points upon victory)
• common enemies, which deal 1 points of damage to Ernesto and may be slain for experience points
  
  • bats (take 1 hit to kill, generate 1 XP)
    
  • snakes (take 2 hits to kill, generate 2 XP, poison Ernesto if he’s not immune to poison)
    
  • fanatics (take 2 hits to kill, generate 3 XP)
• bosses, which deal 2 points of damage to Ernesto (except for the final God which deals 3)
  
  • Golems (optional bosses in both levels 2 and 3; take 4 hit points or 1 hit point with the Golem Killer to kill, generate 4 XP)
    
  • Dungeon Gods (mandatory bosses in levels 4; take 4 hit points with Severance to kill, generate 4 XP)
• weapons, which allow Ernesto to fight the bosses of levels 2, 3, and 4 but do not affect common enemies
  
  • Golem Killer (may be equipped to slay the golems in levels 2 and 3 even when Ernesto’s attack power is less than 4)
    
  • Severance (must be equipped to slay the three gods of level 4)
• equipment
  
  • tools (disarm mechanical traps)
    
  • oracles (reveal the positions of hidden pit traps)
    
  • antidotes (cure Ernesto of poison and grant him immunity if and only if Ernesto is already poisoned)
    
  • templar outfits (allow Ernesto to pass among fanatics without engaging in combat)
• miscellany
  
  • tunnels (may be a free space or may be a pit trap dealing 2 damage to Ernesto)
    
  • toxic gas clouds (poison Ernesto if he’s not immune to poison)
    
  • signs (have no apparent effect)

Level 4 generates in only one configuration. Ernesto will always have access to two medkits at the outset and then face (in order):

1. 1 fanatic (dealing 1 damage)
   
2. 1 toxic gas (dealing 1 damage unless Ernesto is immunized)
   
3. 2 Dungeon Gods (each dealing 2 damage)
   
4. 1 Dungeon God (dealing 3 damage)

It's relatively difficult to reach this point without gaining immunity to poison (see antidote above), so Ernesto is probably looking at 8 points of damage. He must keep 1 at all times and can gain 2 from medkits, so victory should be ensured if Ernesto exits level 3 with either 7 health points or 6 health points and a templar outfit. Ernesto may be able to survive with 1 point fewer if he ends level 3 with enough XP to level-up during the course of level 4 (this is the case in most playthroughs when Ernesto does not wear the templar outfit).

Equally important to Ernesto's health level is the weapon he holds upon exiting Level 3. If he is not equipped with Severance ("the god killer"), he will not be able to pass any Dungeon God and he will die immediately upon his encounter with the first.

As an unfinished game, Ernesto has some quirks that are worth noting:

• Ernesto’s starting weapon is a whip that has no function.
  
• Tile descriptions will not display until Ernesto selects a start point.
  
• Tunnels are potentially lethal at the start of level 1. A single pit trap will kill Ernesto immediately and without warning.
  
• Even when Ernesto has consulted an oracle and revealed the locations of all pit traps, safe tunnels remain marked with a question mark.
  
• The description of the tool says that it can unlock doors, but there are no doors in the game.
  
• Since poison gas does not appear on level 1, Ernesto will usually be immunized before he encounters it, making it superfluous in most playthroughs.
  
• Donning a templar outfit is rarely advantageous: in most cases, the loss of potential XP outweighs the savings of health points. Fortunately, Ernesto cannot don a templar outfit if he is currently poisoned, and he will discard his templar outfit if he is confronts a bat, snake, or god, or if he is poisoned by gas. (Ernesto will remain in disguise if he faces a Golem or he encounters gas while already immunized.)
  
• Signs have no function.
  
• If Ernesto confronts a Dungeon God while wielding the Golem Killer, the game-over text is repeated so many times that it runs off the window.