feat: port machine gun (#954)

This PR closes #573.

I added `bullet_spread` system to the machine gun because I think it
balances the game and looks good, and added `empty_cooldown` because it
would be really boring if `gun_empty.ogg` kept playing at the same
frequency as the normal cooldown, so in this gun we have the shooting
cooldown and the empty sound cooldown. I also made a very slight change
in the main system for using items because it had to be able to shoot
constantly, so now you can keep shoot input pressed with any weapon.

Something I think is important to mention is that the shooting animation
is synchronized to the rate of fire, so if you change the rate of fire
the animation will also change. It could be easily changed with a new
variable in the .yaml so let me know whether you think it should be
faster or slower.

The machine gun has two states (idle and shooting) and its only function
is to reset and start animations.

assets/elements/item/machine_gun/bullet/machine_gun.bullet.yaml

@@ -0,0 +1,11 @@
+lifetime: 0.65
+speed: 650
+body_diameter: 15
+atlas: ./machine_gun_bullet.atlas.yaml
+
+explosion_fps: 12
+explosion_frames: 3
+explosion_volume: 0.025
+explosion_lifetime: 0.4
+explosion_sound: ../explosion/bullet_hit_dull.ogg
+explosion_atlas: ../explosion/explosion.atlas.yaml

assets/elements/item/machine_gun/bullet/machine_gun_bullet.atlas.yaml

@@ -0,0 +1,4 @@
+image: ./machine_gun_bullet.png
+tile_size: [30, 4]
+rows: 1
+columns: 1

assets/elements/item/machine_gun/explosion/explosion.atlas.yaml

@@ -0,0 +1,4 @@
+image: ./explosion.png
+tile_size: [11, 11]
+rows: 1
+columns: 4

assets/elements/item/machine_gun/machine_gun.atlas.yaml

@@ -0,0 +1,4 @@
+image: ./machine_gun.png
+tile_size: [80, 24]
+rows: 2
+columns: 2

assets/elements/item/machine_gun/machine_gun.element.yaml

@@ -1,2 +1,3 @@
-name: Machine Gun
+name: MachineGun
 category: Weapons
+data: machine_gun.yaml

assets/elements/item/machine_gun/machine_gun.yaml

@@ -0,0 +1,21 @@
+atlas: ./machine_gun.atlas.yaml
+
+max_ammo: 25
+cooldown: 125ms
+empty_cooldown: 600ms
+bullet_meta: ./bullet/machine_gun.bullet.yaml
+bullet_spread: 0.1
+
+shoot_sound_volume: 0.1
+shoot_sound: ./shoot/shoot.ogg
+empty_shoot_sound_volume: 0.1
+empty_shoot_sound: ./shoot/gun_empty.ogg
+
+bounciness: 0.3
+can_rotate: true
+body_size: [32, 8]
+fin_anim: grab_2
+angular_velocity: 0.1
+throw_velocity: 360
+grab_offset: [13, -3]
+kickback: 75

assets/game.yaml

@@ -346,6 +346,7 @@ core:
     - /elements/item/jellyfish/jellyfish.element.yaml
     - /elements/item/kick_bomb/kick_bomb.element.yaml
     - /elements/item/mine/mine.element.yaml
+    - /elements/item/machine_gun/machine_gun.element.yaml
     - /elements/item/musket/musket.element.yaml
     - /elements/item/buss/buss.element.yaml
     - /elements/item/periscope/periscope.element.yaml

assets/map/levels/level_7.map.yaml

@@ -1173,7 +1173,7 @@ layers:
   - pos:
     - 216.0
     - 310.5
-    element: /elements/item/musket/musket.element.yaml
+    element: /elements/item/machine_gun/machine_gun.element.yaml
   - pos:
     - 248.0
     - 438.5

src/core/elements.rs

@@ -15,6 +15,7 @@ pub mod flappy_jellyfish;
 pub mod grenade;
 pub mod jellyfish;
 pub mod kick_bomb;
+pub mod machine_gun;
 pub mod mine;
 pub mod musket;
 pub mod periscope;
@@ -31,9 +32,9 @@ pub mod urchin;
 pub mod prelude {
     pub use super::{
         buss::*, crab::*, crate_item::*, decoration::*, fish_school::*, grenade::*, jellyfish::*,
-        kick_bomb::*, mine::*, musket::*, periscope::*, player_spawner::*, slippery::*,
-        slippery_seaweed::*, snail::*, spike::*, sproinger::*, stomp_boots::*, sword::*, urchin::*,
-        *,
+        kick_bomb::*, machine_gun::*, mine::*, musket::*, periscope::*, player_spawner::*,
+        slippery::*, slippery_seaweed::*, snail::*, spike::*, sproinger::*, stomp_boots::*,
+        sword::*, urchin::*, *,
     };
 }
 
@@ -316,6 +317,7 @@ install_plugins!(
     jellyfish,
     kick_bomb,
     mine,
+    machine_gun,
     musket,
     buss,
     player_spawner,

src/core/elements/buss.rs

@@ -188,14 +188,15 @@ fn update(
             // If the item is being used
             let item_used = items_used.remove(entity).is_some();
             if item_used && buss.cooldown.finished() {
+                // Reset fire cooldown
+                buss.cooldown = Timer::new(*cooldown, TimerMode::Once);
                 // Empty
                 if buss.ammo.eq(&0) {
                     audio_center.play_sound(*empty_shoot_sound, *empty_shoot_sound_volume);
                     continue;
                 }
 
-                // Reset fire cooldown and subtract ammo
-                buss.cooldown = Timer::new(*cooldown, TimerMode::Once);
+                // Subtract ammo
                 buss.ammo = buss.ammo.saturating_sub(1).clamp(0, buss.ammo);
                 audio_center.play_sound(*shoot_sound, *shoot_sound_volume);