Roguelike design — and the Tunnel Rat concept

How to build a roguelike on the Deckline: what the genre actually is (factored, so you can pick the parts), the fairness ethic that makes permadeath fun, the grid tactics, the constrained-glyph bestiary, item identification, and the keyboard-first quality-of-life aids — then a worked candidate cart, Tunnel Rat.

Sources: John Harris, Exploring Roguelike Games (CRC Press, 2021) — the practical bible; and the IJEMS 2022 player-psychology paper (permadeath as the engine of meaning; the frustration→mastery loop is the retention mechanic).

Authority / neighbours: world-engine.md (procedural worlds), maps.md (tunnels are a .map), ADR-0047 (the experience tier — the drone loop), ADR-0045 (the pursuit substrate — ICE), synthesis-atari-graphics.md (mono→dither; the pursuit-AI mechanic), screen-design-rules.md. Build task: GWP-674.

0. Why roguelikes fit the Deckline

Almost every defining roguelike trait is something the deck already is:

Procedural worlds → the World Engine (“random within form”).
Grid-based → the 128×75 cell grid; entities take one cell.
ASCII display → amber-on-black is the roguelike native look, not a retro affectation.
Turn-based → fits a keyboard-first, contemplative deck (no twitch reflexes; you take your time).
Permadeath → maps onto the run/save model; loss is the point, not a bug.

The IJEMS paper’s takeaway: permadeath + difficulty + scarce saving turn play into a journey where the player cycles blame → anger → negotiation → acceptance → mastery. That arc is the retention loop. The deck is built for exactly this kind of deliberate, high-stakes play.

1. What a roguelike is — the Berlin Interpretation

The canonical definition is factored, not a checklist (Harris Ch. 7). It splits traits into High- and Low-value factors, and explicitly accepts that good roguelikes can skip some. Use it to decide which knobs a cart turns on.

Factor	What it means	Deck fit / Tunnel Rat
Random environment (High)	World generated for replayability; item placement random	✓ World Engine generates the tunnels
Permadeath (High)	Start over on death; saves are “suspend saves,” deleted on load	✓ run model
Turn-based (High)	One command = one action; not time-sensitive	✓ recommended for the deck
Grid-based (High)	Uniform tile grid; one entity per tile	✓ cell grid
Non-modal (High)	Move/fight/act in one mode; every action always available	aim for it (shops/menus are the usual violations)
Complexity (High)	Several solutions to a goal via item/monster/item-item interactions	the design target (tool/ICE interactions)
Resource management (High)	Manage limited resources (food, potions)	✓ drone power / heat / bandwidth
Hack’n’slash (High)	Killing things matters; player-vs-world (no monster/monster diplomacy)	✓ ICE are obstacles
Exploration & discovery (High)	Careful exploration + learning unidentified items, anew each run	✓ the core loop
Single-player / ASCII / dungeons / numbers / monsters-like-player / tactical (Low)	Nice-to-haves; Harris discounts ASCII as a priority	mostly ✓ by default

Roguelike vs roguelite: Harris reserves roguelike for terminal/turn-based games with randomized worlds + permadeath; roguelite for games that keep randomization + permadeath but drop turn-basis (action/real-time). For the deck, lean roguelike (turn-based) — it suits keyboard-first contemplative play. (This is a per-cart decision; see §7.)

2. The design ethic: fairness under permadeath

Permadeath only feels fair if the game is designed for it. The dictum (Harris Ch. 6), worth memorizing:

The First Law of Roguelike Design: Provided reasonable play, the player’s character should not be killed or suffer great permanent harm in one attack.

“Reasonable play” = the developer’s intended normal style — not paranoid play (searching every tile against instadeath traps). Corollaries:

Critical moments. Most turns aren’t dangerous; a few are “in check” — one wrong move ends the run. The craft is making critical moments recognizable and escapable, and never springing an unavoidable one-shot under reasonable play.
Escape tools. Provide a spread — one-use, multi-use, infinite, equippable — so a cornered player has options (flee, blink, stun, wall-off).
Push back criticality. Improving state (more HP, speed, vision/detection) makes once-deadly situations survivable. Progression is widening the safety margin.
Procedural fairness is the author’s burden. Hand-built levels can avoid unfair setups; a generator can’t, so the rules (entities, tools, sight) must guarantee survivability across whatever the generator produces. Even “instadeath” monsters in NetHack obey the Law because the player has usually had a chance to gain the relevant defense.

3. Gridland tactics (the moment-to-moment loop)

The genre’s tension lives in grid movement (Harris Ch. 4):

Diagonals. Diagonal moves cost the same as orthogonal; cut corners (a zig-zag corridor is walked straight diagonally). Enemies exploit this — round a corner into the corner cell and the chaser gets a free hit. Movement is tactics.
Line of sight — the key primitive. Ranged/caster enemies “cannot attack what they can’t see.” Breaking LOS around a corner forces them to close to melee. On the deck this reskins perfectly: ICE can’t trace what it can’t see — duck behind a node and the sentry has to come to you.
Doors as a resource → firewalls. A door isn’t just an obstacle; close/lock it to block (handless) pursuers. Reskin: a firewall you raise/lower to wall off a subnet.
Speed: world-centric, not player-centric. Schedule actors on a tick clock (an actor acts every N ticks) rather than “monsters move per player move.” This is exactly the World Clock — reuse it; it also resists the flee-hit-flee exploit.
Escape, regeneration, loops. Characters heal fast by resting; flee to a new level to escape (some pursuers don’t follow); kite tough foes around a loop or pillar to heal between hits. “He who fights and runs away, lives to flee another day.”

4. The bestiary in a constrained glyph set (the “Letter Q” problem)

Roguelikes represent a whole bestiary in ~26 letters — solved with case (upper/lower = different species), color, a few symbols (@ human, & demon, : lizard), and terrain-disguise (mimics, ghosts as blank cells). The constraint becomes a theme (Rogue adds one monster per level; dragons at 22; the Amulet at 26).

The deck has the same constraint, sharper: a mono amber Code Page (256 glyphs) plus the soft-glyph plane, but no colour. So:

Shape carries the load. With no colour channel, distinguish entities by glyph shape + the legend (the same legend mechanism as maps.md §4 — tile/entity code → glyph + semantics).
Soft-glyph for custom creatures. Use the soft-glyph plane for bespoke ICE/creature glyphs beyond the Code Page.
State via inverse / dither. “Alerted,” “damaged,” “cloaked” → inverse video or dither density (mono→dither, per synthesis-atari-graphics.md), not colour.
Lean into the theme. A constrained roster is a feature: a tight, legible bestiary reads better than a sprawl.

5. Item identification — “part hack and slash, part scientific method”

A defining pillar (Harris Ch. 1): unknown items (potions/scrolls/wands) have scrambled-but-consistent appearances within a run — you learn them by experiment (or an identify tool), at some risk. Discovery-anew-each-run is half the replayability.

The cyberpunk reskin writes itself: unidentified exploits / payloads / daemons. A scavenged payload might open a port, heal the drone, or brick it — you don’t know until you run it (or burn a scan tool). Appearances are consistent within the run (“the jagged-sigil payload” is always the same this run). This is the deck-native version of the unknown-potion loop, and it’s the most characterful roguelike pillar — keep it.

6. Quality-of-life travel aids (for a keyboard-first deck)

Modern roguelikes (Crawl, Harris Ch. 28) remove movement tedium — and the deck, being keyboard-first (the nEmacs lineage), should ship these from the start:

Auto-explore — pathfind to the nearest unexplored cell, auto-pick-up useful items, halt the instant anything interesting appears (monster/trap/item). Turns the game into a “situation generator,” focusing attention on decisions, not steps.
Autotravel — go to a known location or branch by pathfinding; cycle stairs/exits by distance.
Search / stash — remember every item’s location; text-search to recall “where was that payload?”
Legibility coding → mono: bad/useless/special items distinguished by glyph + inverse + dither (Crawl uses red/gray/white; we use shape/brightness).

These aren’t cheating — when a feature makes you wonder how you played without it, it’s fixing a real friction.

7. The Tunnel Rat concept (a worked candidate, not committed)

Tunnel Rat — drive a drone through procedurally-generated tunnels to gain access to other ports/networks. A net-infiltration roguelike.

It’s a dungeon crawl wearing a cyberpunk skin, and the reskin is clean:

Roguelike	Tunnel Rat
`@` adventurer	the drone
corridors / rooms	tunnels / nodes
dungeon levels / branches	ports / subnets
the Amulet (goal)	target data / root access
monsters	ICE / sentries / daemons (pursuit-AI, ADR-0045)
unidentified items	scavenged exploits / payloads (§5)
doors	firewalls (§3)
HP / food	drone integrity / power / heat
permadeath	the drone is traced and fried — lose the run

Which Berlin knobs (recommended): turn-based · grid · procedural (World Engine) · permadeath (run) · resource management (power/heat) · complexity (tool↔ICE interactions) · identification (unknown payloads). I.e. a roguelike, not a roguelite.

KN-86 stack ties: tunnels are a .map (maps.md) generated by the World Engine; the drone control loop is an experience-tier surface (ADR-0047); ICE behaviour is the pursuit-AI mechanic (the games-book thread in synthesis-atari-graphics.md, GWP-658); CIPHER can voice the trace/alert flavour.

Open decisions (for Josh, not pre-locked):

Turn-based vs real-time (roguelike vs roguelite). Recommendation: turn-based.
Permadeath model — full per-run permadeath vs a run with meta-progression (salvage/reputation carried in Universal Deck State); how a fried drone reconciles with the offline-first save model.

8. Build roadmap (→ GWP-674)

A vertical slice, in dependency order:

Procedural tunnel level — World Engine → a .map (cave/BSP/drunkard’s-walk; “random within form”).
Drone movement + LOS — grid move (diagonals), line-of-sight as the core tactical primitive.
ICE archetypes — 2–3 behaviours on the pursuit-AI (chaser, ranged/tracer that LOS-breaks defeat, sentry).
One unidentified-payload interaction — the scientific-method hook.
Trace / permadeath fail state.
QoL — auto-explore at minimum.

Deps: the map system (GWP-672), the mechanics/pursuit-AI (GWP-658), the World Engine, the experience tier (ADR-0047).

9. How agents should use this guide

Designing any roguelike/roguelite cart? Start from the Berlin factors (§1) — decide which knobs, don’t cargo-cult the whole list. State the roguelike-vs-roguelite choice explicitly.
Obey the First Law (§2): no one-shot death under reasonable play; make critical moments recognizable + escapable; ship escape tools.
Grid tactics (§3): LOS is the core primitive (ICE can’t trace what it can’t see); doors=firewalls; reuse the World Clock for world-centric ticks.
Bestiary (§4): shape + soft-glyph + legend (no colour); state via inverse/dither.
Keep item identification (§5) — it’s the most characterful pillar, and it reskins to exploits.
Ship the QoL aids (§6) — the deck is keyboard-first; auto-explore/travel/search are table stakes.
Tunnel Rat (§7) is a candidate, not a commitment — surface the open decisions before building.