seed_crack/
seed_crack.rs

1use gdlib::{
2    cclocallevels::{
3        gdlevel::GDLevel,
4        gdobj::{
5            GDObject,
6            ids::{objects::TRIGGER_ADVANCED_RANDOM, properties::RANDOM_PROBABILITIES_LIST},
7            structs::Group,
8        },
9    },
10    core::rand::{check_seed_advanced_random, next_seed_mut},
11};
12
13fn main() {
14    let level = GDLevel::from_gmd("test_gmds/Chompstep.gmd").unwrap();
15    let mut objects = level.get_decrypted_data().unwrap().objects;
16
17    // filter out all objects that are not advanced random triggers
18    objects.retain(|o| o.id == TRIGGER_ADVANCED_RANDOM && o.config.pos.0 > 0.0);
19    objects.sort_by(|a, b| a.config.pos.0.total_cmp(&b.config.pos.0));
20
21    // the group we want spawned for each trigger
22    // -1: any group is fine
23    let expected = vec![
24        2, -1, 2, -1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -1, 2, 2, 2, 2, 2,
25        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
26    ];
27    let mut seed = 0;
28
29    // then try all of the seeds
30    // cap it out at 25 seeds because searching all of them is impractically slow on a CPU
31    while !crack_seed(seed, &expected[..25], &objects) {
32        seed += 1;
33        if seed % 1000000 == 0 {
34            println!("checked seeds until {seed}");
35        }
36    }
37
38    // the seed you get is guaranteed to get you to 79% on Chompstep
39    println!("got seed: {seed}");
40}
41
42fn crack_seed(seed: u64, expected: &[i16], objects: &Vec<GDObject>) -> bool {
43    let mut seed_clone = seed;
44
45    for (idx, obj) in objects.iter().enumerate() {
46        if idx == expected.len() {
47            return true; // stop when we run out of expected groups to check
48        }
49        if expected[idx] == -1 {
50            continue; // any group is fine (-1 is the sentinel value)
51        }
52
53        if !check_object(seed_clone, obj, expected[idx]) {
54            return false;
55        }
56        // update seed (since adv rand triggers do it)
57        next_seed_mut(&mut seed_clone);
58    }
59
60    true
61}
62
63fn check_object(seed: u64, object: &GDObject, expected_group: i16) -> bool {
64    let probabilities = object.get_property(RANDOM_PROBABILITIES_LIST).unwrap();
65
66    match check_seed_advanced_random(seed, &probabilities) {
67        Some(Group::Regular(g)) => g == expected_group,
68        _ => false, // this should never be hit since all of the triggers have set groups
69    }
70}
seed_crack/seed_crack.rs

seed_crack/
seed_crack.rs
