#![allow(unused_variables)]
fn main() {
    use std::collections::BTreeMap;
    let mut player_stats = BTreeMap::new();
    fn random_stat_buff() -> u8 {
        42
    }
    player_stats.entry("health").or_insert(100);
    player_stats.entry("defence").or_insert_with(random_stat_buff);
    let stat = player_stats.entry("attack").or_insert(100);
    *stat += random_stat_buff();
    player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
}