Settings that steer the RNG¶

The original game has one gameplay RNG (crt_rand). Spawns, drops and AI draw from it, but so do presentation paths: hit sounds, the music playlist, blood and particles. Anything that gates one of those presentation paths changes which draws happen, and from then on every spawn and drop. Machine state and options can therefore change how a run plays out.

We found this when a Windows machine lost its audio device. The original game failed to start music, and its RNG stream stopped matching the port's.

Policy for the port and ranked play: every such input is either fixed in place, with the sim assuming the canonical value and never reading the real one, or recorded in the replay and pinned for ranked runs. Add newly found gates here.

Gate	Original behavior	Port
Audio	see Audio	fixed: assumes audio works
Game tune latch	global, cleared by every other track	per-run flag, clear at run start
Detail preset (1..5)	effect spawns draw per preset	recorded; ranked runs need 5
Violence disabled	blood and particle paths draw or skip	recorded; ranked runs need violence on
Attract mode	`demo_mode_active` skips the game tune	removed: runs are never attract mode
Frames outside gameplay	one discarded draw per frame	fixed: none
Corpse fading (`cv_bodiesFade`)	off frees a corpse's slot the frame it dies	fixed: corpses fade
Weapon history	a used weapon costs an extra draw in the drop reroll	recorded; ranked runs start with none
Quest retries	each failure softens the next attempt's creatures	recorded; ranked runs play as the first try
Seed	the session RNG carries into the next run	recorded; ranked runs draw a fresh seed
Screen size and pad reach	the cursor is clamped to the screen; pad reach follows `cv_padAimDistMul`	the aim is recorded; ranked runs bound it to a 1024x768 view and the default reach

Audio¶

The first eligible bullet or secondary-projectile hit of a run (projectile_update, not in Rush) calls music_play_exclusive(music_track_game_playlist) instead of playing its hit sound while music_playlist_randomized_latch is clear. music_play_exclusive returns early unless all of the following hold:

audio initialized (music_ready, set by audio_init_music)
sound and music are enabled in the config
the playlist is not empty (music\game_tunes.txt queued tracks)
no plugin runtime is active

Only then does it draw crt_rand() % music_playlist_entry_count and set the latch. With the gate open, a run draws once for the playlist, then one hit-sound rand per later hit. With the gate closed the latch never sets, so every hit takes the tune branch and draws nothing.

The port always takes the open-gate path (WorldStepRuntime and WorldState hit audio, GameplayState.game_tune_started). Its sound and music options only mute output. Recorded runs, and their verification, do not depend on the player's audio device or settings.

Game tune latch¶

The latch is global, not per run. Any other music_play_exclusive call clears it (with the audio gate open), and every route into a run passes one: startup, pause to main menu, game over, quest results and quest failed. So it is clear at every run start, which the port's per-session flag models. The one unmodeled clear is the quest completion music at 2000 ms into the completion transition. No hit can land then, because no creatures are left.

Detail and violence¶

Both are recorded run inputs, so replays verify under any value and a run at low detail plays exactly as the original does at low detail. The leaderboard ranks only runs in the ranked profile, which pins these and the other recorded gates above; runs outside it still verify, they just do not rank.

Frames outside gameplay¶

game_frame_update ends every frame with a discarded crt_rand(), whatever the state. Each port tick carries its gameplay frame's draw. Pause, the perk menu and the menu's slide-in and slide-out frames draw too, and their count depends on wall-clock time and frame rate, so waiting in a menu changes the stream. The port fixes those frames at zero.