Roguelike

A playbook for roguelikes — the turn engine, procedural dungeons, field-of-view, permadeath,
and run economy. This is a compositional skill: it orchestrates procedural generation,
tilemaps, save handling, and AI into a run-based game. It does not re-teach noise/RNG or
tilemap APIs; it defines the loop and the systems that make a run compelling.

When to use

• Use when building a turn-based, grid-based dungeon crawler where each death ends the
  run and the world is regenerated — a roguelike or "roguelite" (with meta-progression).
• Use when designing procedural dungeons, FOV/fog-of-war, permadeath stakes, or loot tables.

When not to use: real-time action with roguelike dressing → build the action genre
(platformer/fps-shooter) and layer procedural-gen. Deep stats/quests/dialogue without
permadeath → rpg. Open-world needs/crafting → survival-crafting.

What makes it a roguelike (design anchor)

The community reference is the Berlin Interpretation (RogueBasin, IRDC 2008): a set of
"roguelikeness" factors, not a checklist. The high-value ones are the design targets:
random environment generation, permadeath, turn-based, grid-based, non-modal (all actions
in one mode), complexity (many item/monster interactions), resource management,
hack-and-slash, and exploration & discovery. Lean into these to feel roguelike; pick
which to keep deliberately. "Roguelite" usually relaxes permadeath with meta-progression.

Core loop

Take a turn (move / fight / use) → the world resolves its turn → see new state → descend /
loot / survive → die and restart with a fresh dungeon. Replayability comes from the world
changing each run, not the player memorizing a fixed layout.

Must-have systems

1. Turn scheduler — energy/initiative system so fast actors act more often (Pattern 2).
2. Grid map + movement — tile coordinates; bump-to-attack; blocked/walkable queries.
3. Procedural dungeon generator — rooms + corridors, or BSP/cellular; guarantee connectivity.
4. Field of view + explored memory — what's visible now vs. seen-before (Pattern 3 / refs).
5. Combat + entities — HP, attack/defense, status; monsters obey the same rules as the player.
6. Loot + drop tables — weighted, depth-scaled item/monster spawning (refs).
7. Permadeath + (optional) meta-progression — wipe the run; persist only unlocks/score.
8. Message log + clear UI — the player reasons from text/state; surface numbers and events.

Design knobs

Patterns

1. Deterministic, seedable run RNG

# Pseudocode. One seeded RNG per run makes dungeons reproducible (daily runs, bug repro).
run_seed = chosen_seed or random_seed()
rng = Rng(run_seed)                 # use your engine's seedable RNG, not global random
dungeon = generate_dungeon(rng, depth)   # same seed + depth => same dungeon
# Persist run_seed in the save so a crash can resume the same world (see save-systems).

2. Energy-based turn scheduler (speeds differ)

# Pseudocode. Each actor gains energy each tick and acts when it has enough.
# Faster actors gain more per tick, so they act more often — no fixed "player then enemies".
TURN_COST = 100
def next_actor(actors):
    while True:
        for a in actors:                 # stable order avoids ties favoring one side
            a.energy += a.speed          # e.g. speed 100 = normal, 150 = hasted
            if a.energy >= TURN_COST:
                a.energy -= TURN_COST
                return a                 # this actor takes exactly one action now

3. Field of view + explored memory

# Pseudocode. Recompute visibility from the player each time they move.
visible = compute_fov(map, player.pos, radius=8)   # symmetric shadowcasting (see refs)
for cell in visible:
    explored.add(cell)                  # remember it forever (dim "fog of war")
# Render: visible -> lit; explored-but-not-visible -> dim; never-seen -> hidden.

Use a proven FOV algorithm (recursive shadowcasting or symmetric shadowcasting). Do not
roll a naive raycast-per-cell — it produces asymmetric, "blinking" vision. See refs.

Pitfalls / failure modes

• Disconnected dungeons → rooms the player can't reach. Always run a connectivity/flood-fill
  pass and carve corridors until every walkable cell is reachable.
• Naive FOV → vision that flickers or is asymmetric (you see them, they don't see you).
  Use shadowcasting; test symmetry.
• Real-time loop pretending to be turn-based → input races and double-moves. Resolve one
  discrete turn at a time; queue input.
• Flat difficulty → no descent pressure. Scale monsters/loot by depth and keep resources scarce.
• Permadeath that wipes meta-unlocks → frustration. Separate run state (wiped) from
  profile state (unlocks, scores) when saving (see save-systems).
• Save-scumming a "permadeath" game → delete or invalidate the run save on load if you want
  true permadeath; keep only the profile.
• Unreadable state → the player can't plan. Show HP, turn results, and a message log.

Composition (build it from these skills)

• Generation: procedural-gen (noise, seeded RNG, dungeon/room algorithms) — the engine of replayability.
• Map rendering: godot-tilemap / unity-tilemap-2d for the grid; level-design for set-piece rooms/vaults.
• Enemies: game-ai for monster decision-making (often simple on a grid: seek/flee/patrol).
• Persistence: save-systems for run-resume, profile/meta-progression, and true permadeath wipes.
• Scripting/data: godot-resources / unity-scriptableobjects to define items, monsters, and drop tables as data.
• UI: godot-ui-control for the message log, inventory, and HUD.
• Feel: game-feel for hit/death juice — screen shake and hit-stop that sell impacts on a turn-based grid.

References

• For dungeon-generation algorithms (rooms-and-corridors, BSP, cellular automata, connectivity),
  FOV (shadowcasting), and weighted loot/spawn tables, read references/generation-fov-loot.md.