Tool Automatically Detects and Patches Softlocks in Classic Sierra SCI Games

Automated Softlock Detection

A new static analysis tool has been developed to address "walking-dead states" in classic Sierra SCI adventure games. These states, also known as softlocks, occur when a player can still interact with the game but has unknowingly made progress towards victory impossible. The tool decompiles the game's scripts and uses abstract interpretation to map out guarded room transitions, item movements, and plot-flag writes.

Patch Generation and Installation

Upon identifying a softlock, the tool automatically derives and verifies guards that prevent players from entering these unwinnable situations. These guards are then compiled and installed into the game. The system operates autonomously, discovering critical game elements such as the start room, victory room, death signals, and debug flags directly from the game's code, eliminating the need for manual configuration per title.

Tested Games

The tool has been successfully applied and play-tested on four Sierra SCI games: Leisure Suit Larry 2 (SCI0, 1988), King's Quest IV (SCI0, 1988), King's Quest VI (SCI1.1, 1992), and Laura Bow 2 (SCI1.1, 1992). These tests confirmed its ability to function across different versions of the SCI engine without requiring game-specific analysis code. For example, in King's Quest IV, the tool patched issues related to a whale, a night clock, and seven stranded items.

Example of a Patch

One example cited involves Leisure Suit Larry 2, where the analyzer identified a one-way ship boarding sequence that could lead to a softlock if essential items were not carried. The tool determined which items were necessary, re-verified the guarded model to ensure no new softlocks were introduced, and recompiled the affected scripts into Sierra's loose-patch format. This allows the game to refuse a crossing if a critical item, like sunscreen, is missing, or if a detrimental item, such as spinach dip, is being held.