Particle effects: falling trails behind projectiles, exploding fireballs and cannonballs, arrows stuck in walls and floors

- projectiles get styles: arrows (shaft and fletching), cannonballs and fireballs fly in an arc, shadow, holy, arcane, rune and magic bolts with their own glow
- trails of embers, sparks, motes or smoke that drift down to the floor
- fireballs explode on the ground (flash, shock wave, embers, smoke, scorch mark), cannonballs burst into stones, dirt, sparks and smoke
- arrows stay stuck in walls (or glance off into the floor) for five minutes, at most 400; they drop out when the wall is dug away
- spells: lightning sprays sparks and scorches the floor, healing lifts green motes, level-ups and summoning rain sparkles; digging throws earth, gold pops coins
- particles are never saved and use their own random numbers

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/game.rs

@@ -379,6 +379,7 @@ pub struct Fx {
     pub h: f32,  // height of the start point (3D)
     pub h2: f32, // height of the end point (projectiles)
     pub size: f32, // 1 = normal; attacks of higher levels look bigger
+    pub style: u8, // projectiles: arrow, cannonball, fireball, ... (see particles.rs)
 }
 
 #[derive(Serialize, Deserialize)]
@@ -446,6 +447,12 @@ pub struct Game {
     #[serde(skip)]
     pub springs: usize, // claimed mana springs (recounted)
     #[serde(skip)]
+    pub parts: Vec<crate::particles::Part>, // visual particles (never saved)
+    #[serde(skip)]
+    pub stuck: Vec<crate::particles::Part>, // arrows stuck in walls and floors, scorch marks
+    #[serde(skip, default = "crate::particles::vrng")]
+    pub vrng: Rng, // random numbers for the particles only
+    #[serde(skip)]
     pub demo: Option<crate::demo::Demo>, // the endless bridge battle behind the title menu
     #[serde(default)]
     pub dwarf_caves: Vec<crate::dwarves::DwarfCave>,
@@ -606,6 +613,9 @@ impl Game {
             springs: 0,
             freed: 0,
             demo: None,
+            parts: Vec::new(),
+            stuck: Vec::new(),
+            vrng: crate::particles::vrng(),
             dwarf_caves: Vec::new(),
             dwarf_t: 30.0,
             rune_free: 0,
@@ -922,8 +932,9 @@ impl Game {
 
     pub fn fx(&mut self, kind: u8, x: f32, y: f32, x2: f32, y2: f32, max: f32, col: u32) {
         let h = if kind == 0 { 0.45 } else { 0.4 };
+        self.fx_particles(kind, x, y, h, col);
         if self.fx.len() < 400 {
-            self.fx.push(Fx { kind, x, y, x2, y2, t: 0.0, max, col, h, h2: 0.45, size: 1.0 });
+            self.fx.push(Fx { kind, x, y, x2, y2, t: 0.0, max, col, h, h2: 0.45, size: 1.0, style: 0 });
         }
     }
 
@@ -931,7 +942,7 @@ impl Game {
     #[allow(clippy::too_many_arguments)]
     pub fn shot(&mut self, x: f32, y: f32, h: f32, x2: f32, y2: f32, h2: f32, max: f32, col: u32) {
         if self.fx.len() < 400 {
-            self.fx.push(Fx { kind: 0, x, y, x2, y2, t: 0.0, max, col, h, h2, size: 1.0 });
+            self.fx.push(Fx { kind: 0, x, y, x2, y2, t: 0.0, max, col, h, h2, size: 1.0, style: 0 });
         }
     }
 
@@ -944,8 +955,9 @@ impl Game {
 
     // effect at a given height
     pub fn fx_at(&mut self, kind: u8, x: f32, y: f32, h: f32, max: f32, col: u32) {
+        self.fx_particles(kind, x, y, h, col);
         if self.fx.len() < 400 {
-            self.fx.push(Fx { kind, x, y, x2: 0.0, y2: 0.0, t: 0.0, max, col, h, h2: h, size: 1.0 });
+            self.fx.push(Fx { kind, x, y, x2: 0.0, y2: 0.0, t: 0.0, max, col, h, h2: h, size: 1.0, style: 0 });
         }
     }
 
@@ -961,6 +973,7 @@ impl Game {
             self.step(dt);
         }
         self.sync_treasury();
+        self.update_particles(dt);
         for f in self.fx.iter_mut() {
             f.t += dt;
         }
@@ -1875,6 +1888,15 @@ impl Game {
             let h = if flies(e.kind) { 0.8 } else { 0.45 };
             self.shot(e.x, e.y, h, tx, ty, 0.45, 0.25, col);
             self.grow_last_fx(lv);
+            use crate::particles::*;
+            self.style_last_fx(match e.kind {
+                EK::Archer => ST_ARROW,
+                EK::Mage => ST_SHADOW,
+                EK::Priest => ST_HOLY,
+                EK::Priestess | EK::Wyrm => ST_FIRE,
+                EK::Owl => ST_ARCANE,
+                _ => ST_PLAIN,
+            });
             self.sfx(Sfx::Shoot, e.x, e.y);
         } else {
             self.fx(2, tx, ty, 0.0, 0.0, 0.25, if e.level >= 9 { 0xff60e0ff } else { 0xffffffff });
@@ -1904,8 +1926,6 @@ impl Game {
         }
         if e.kind == EK::Priestess || e.kind == EK::Wyrm {
             // fireball / fire breath: half damage to enemies around the target
-            self.fx(3, tx, ty, 0.0, 0.0, 0.5, 0xff3080ff);
-            self.grow_last_fx(lv);
             let me = e.side();
             let splash: Vec<usize> = self
                 .ents
@@ -4050,7 +4070,12 @@ impl Game {
             TowerKind::Rune => 0xff40c0ff,
         };
         self.shot(mx, my, mh, ex, ey, eh, 0.3, col);
-        self.fx_at(2, ex, ey, eh, 0.3, 0xffffffff);
+        self.style_last_fx(match t.kind {
+            TowerKind::Arrow => crate::particles::ST_ARROW,
+            TowerKind::Cannon => crate::particles::ST_CANNON,
+            TowerKind::Magic => crate::particles::ST_MAGIC,
+            TowerKind::Rune => crate::particles::ST_RUNE,
+        });
         self.sfx(match t.kind {
             TowerKind::Arrow => Sfx::Shoot,
             TowerKind::Cannon => Sfx::Cannon,
@@ -4123,8 +4148,9 @@ impl Game {
                 TowerKind::Arrow => {
                     // the arrow pierces up to two more heroes behind the target
                     let dir = norm(ex - px, ey - py);
-                    let end = (px + dir.0 * t.range(), py + dir.1 * t.range());
-                    self.shot(mx, my, mh, end.0, end.1, 0.45, 0.3, 0xffd0e0f0);
+                    let (endx, endy, wall) = self.arrow_end(px, py, dir.0, dir.1, t.range());
+                    self.shot(mx, my, mh, endx, endy, 0.45, 0.3, 0xffd0e0f0);
+                    self.style_last_fx(if wall { crate::particles::ST_ARROW_WALL } else { crate::particles::ST_ARROW });
                     self.sfx(Sfx::Shoot, px, py);
                     let mut hits = vec![(j, dmg)];
                     for (o, e) in self.ents.iter().enumerate() {
@@ -4147,8 +4173,7 @@ impl Game {
                 TowerKind::Cannon => {
                     // splash damage and knockback around the impact
                     self.shot(mx, my, mh, ex, ey, 0.4, 0.35, 0xff303030);
-                    self.fx(3, ex, ey, 0.0, 0.0, 0.6, 0xff4070a0);
-                    self.fx(2, ex, ey, 0.0, 0.0, 0.3, 0xff60c0ff);
+                    self.style_last_fx(crate::particles::ST_CANNON);
                     self.sfx(Sfx::Cannon, px, py);
                     let mut hits = Vec::new();
                     for (o, e) in self.ents.iter().enumerate() {
@@ -4176,6 +4201,7 @@ impl Game {
                 TowerKind::Magic => {
                     // sure hit, slows, jumps to a second hero
                     self.shot(mx, my, mh, ex, ey, 0.45, 0.2, 0xffff60d0);
+                    self.style_last_fx(crate::particles::ST_MAGIC);
                     self.sfx(Sfx::Magic, px, py);
                     self.ents[j].slow = 2.0;
                     let chain = self
@@ -4202,6 +4228,7 @@ impl Game {
                 TowerKind::Rune => {
                     // a rune bolt that jumps on to up to three more enemies nearby
                     self.shot(mx, my, mh, ex, ey, 0.45, 0.25, 0xff40c0ff);
+                    self.style_last_fx(crate::particles::ST_RUNE);
                     self.fx(2, ex, ey, 0.0, 0.0, 0.35, 0xffffc040);
                     self.sfx(Sfx::Magic, px, py);
                     let mut hit = vec![j];
@@ -4255,6 +4282,7 @@ impl Game {
                 let dmg = e.atk() * (0.85 + self.rng.f() * 0.3);
                 if s.range > 1.5 {
                     self.shot(e.x, e.y, 0.45, tx, ty, hit_h, 0.25, 0xff70b0d0);
+                    self.style_last_fx(if e.kind == EK::Archer { crate::particles::ST_ARROW } else { crate::particles::ST_PLAIN });
                 } else {
                     self.fx_at(2, tx, ty, hit_h, 0.25, 0xffffffff);
                 }

src/main.rs

@@ -12,6 +12,7 @@ mod i18n;
 mod map;
 mod menu;
 mod platform;
+mod particles;
 mod props;
 mod rival;
 mod render3d;

src/particles.rs

@@ -0,0 +1,353 @@
+// Particles: trails that fall to the ground behind projectiles, explosions of fireballs and
+// cannonballs, bursts of the spells, debris and coins, scorch marks, and arrows that stay stuck
+// in walls and the ground for five minutes. Purely visual: never saved, with their own random
+// numbers (the game's random sequence stays untouched).
+
+use crate::game::*;
+use crate::map::*;
+
+pub const STUCK_MAX: usize = 400; // arrows and scorch marks
+pub const STUCK_LIFE: f32 = 300.0; // seconds an arrow stays
+const PARTS_MAX: usize = 900;
+const GRAVITY: f32 = 6.0;
+
+// particle kinds
+pub const EMBER: u8 = 0; // glowing, falls
+pub const SMOKE: u8 = 1; // rises and grows
+pub const SPARK: u8 = 2; // glowing, falls fast, bounces once
+pub const DEBRIS: u8 = 3; // solid chunk, falls and rests a moment
+pub const MOTE: u8 = 4; // glowing, floats up slowly
+pub const COIN: u8 = 5; // solid gold, bounces
+pub const ARROW: u8 = 6; // stuck arrow (vx, vy, vh = its direction)
+pub const SCORCH: u8 = 7; // dark mark on the floor
+pub const FLASH: u8 = 8; // expanding fireball
+pub const RING: u8 = 9; // shock wave
+
+// projectile styles (Fx::style)
+pub const ST_PLAIN: u8 = 0;
+pub const ST_ARROW: u8 = 1;
+pub const ST_CANNON: u8 = 2;
+pub const ST_FIRE: u8 = 3;
+pub const ST_SHADOW: u8 = 4;
+pub const ST_HOLY: u8 = 5;
+pub const ST_ARCANE: u8 = 6;
+pub const ST_RUNE: u8 = 7;
+pub const ST_MAGIC: u8 = 8;
+pub const ST_ARROW_WALL: u8 = 9; // an arrow that ends in a wall
+
+#[derive(Clone, Copy, Debug)]
+pub struct Part {
+    pub kind: u8,
+    pub x: f32,
+    pub y: f32,
+    pub h: f32,
+    pub vx: f32,
+    pub vy: f32,
+    pub vh: f32,
+    pub t: f32,
+    pub max: f32,
+    pub col: u32,
+    pub size: f32,
+}
+
+pub fn vrng() -> Rng {
+    Rng(0x2545_f491)
+}
+
+// colour as 0xAABBGGRR (like Fx::col)
+pub const fn abgr(r: u8, g: u8, b: u8) -> u32 {
+    0xff00_0000 | (b as u32) << 16 | (g as u32) << 8 | r as u32
+}
+
+// position of a projectile at progress p (cannonballs and fireballs fly in an arc)
+pub fn fx_pos(f: &Fx, p: f32) -> (f32, f32, f32) {
+    let p = p.clamp(0.0, 1.0);
+    let x = f.x + (f.x2 - f.x) * p;
+    let y = f.y + (f.y2 - f.y) * p;
+    let dist = ((f.x2 - f.x).powi(2) + (f.y2 - f.y).powi(2)).sqrt();
+    let arc = match f.style {
+        ST_CANNON => 0.22,
+        ST_FIRE => 0.12,
+        ST_ARROW | ST_ARROW_WALL => 0.04,
+        _ => 0.0,
+    } * dist;
+    let h = f.h + (f.h2 - f.h) * p + arc * (p * std::f32::consts::PI).sin();
+    (x, y, h)
+}
+
+impl Game {
+    fn part(&mut self, kind: u8, (x, y, h): (f32, f32, f32), (vx, vy, vh): (f32, f32, f32), max: f32, col: u32, size: f32) {
+        if self.parts.len() < PARTS_MAX {
+            self.parts.push(Part { kind, x, y, h, vx, vy, vh, t: 0.0, max, col, size });
+        }
+    }
+
+    fn stick(&mut self, p: Part) {
+        if self.stuck.len() >= STUCK_MAX {
+            self.stuck.remove(0);
+        }
+        self.stuck.push(p);
+    }
+
+    // a random direction with the given speed (upwards bias `up`)
+    fn burst_vel(&mut self, speed: f32, up: f32) -> (f32, f32, f32) {
+        let a = self.vrng.f() * std::f32::consts::TAU;
+        let s = speed * (0.4 + 0.6 * self.vrng.f());
+        (a.cos() * s, a.sin() * s, up * (0.5 + self.vrng.f()))
+    }
+
+    fn burst(&mut self, kind: u8, at: (f32, f32, f32), n: usize, speed: f32, up: f32, max: f32, col: u32, size: f32) {
+        for _ in 0..n {
+            let v = self.burst_vel(speed, up);
+            let m = max * (0.6 + 0.6 * self.vrng.f());
+            let sz = size * (0.7 + 0.6 * self.vrng.f());
+            self.part(kind, at, v, m, col, sz);
+        }
+    }
+
+    // particles that come with a new effect (spells, hits, digging, gold, ...)
+    pub(crate) fn fx_particles(&mut self, kind: u8, x: f32, y: f32, h: f32, col: u32) {
+        match kind {
+            // lightning: a shower of sparks, smoke and a burnt spot
+            1 => {
+                self.burst(SPARK, (x, y, 0.1), 40, 3.5, 3.5, 1.0, abgr(255, 250, 200), 0.05);
+                self.burst(SMOKE, (x, y, 0.2), 6, 0.4, 0.6, 2.0, abgr(90, 90, 100), 0.25);
+                self.part(FLASH, (x, y, 0.3), (0.0, 0.0, 0.0), 0.35, abgr(255, 255, 220), 1.0);
+                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 20.0, col: 0, size: 0.8 });
+            }
+            // hit: a few sparks of the effect's colour
+            2 => self.burst(SPARK, (x, y, h.max(0.3)), 5, 1.5, 1.5, 0.5, col, 0.035),
+            3 => self.burst(SMOKE, (x, y, 0.3), 4, 0.3, 0.5, 1.6, abgr(80, 80, 90), 0.2),
+            // healing: green motes rising in a spiral, sparkles falling
+            4 => {
+                for k in 0..12 {
+                    let a = k as f32 * 0.52;
+                    self.part(MOTE, (x + a.cos() * 0.3, y + a.sin() * 0.3, 0.1 + k as f32 * 0.03), (-a.sin() * 0.3, a.cos() * 0.3, 0.9), 1.3, abgr(120, 255, 140), 0.05);
+                }
+                self.burst(EMBER, (x, y, 0.9), 6, 0.6, 0.5, 1.0, abgr(200, 255, 200), 0.03);
+            }
+            // gold: coins pop up and fall
+            5 => self.burst(COIN, (x, y, 0.4), 5, 1.2, 2.5, 1.6, abgr(255, 210, 60), 0.06),
+            // digging: earth chunks
+            6 => self.burst(DEBRIS, (x, y, 0.5), 4, 1.2, 1.5, 1.4, abgr(110, 80, 56), 0.06),
+            // level up, spells, specials: sparkles in the effect's colour shoot up and rain down
+            7 => self.burst(EMBER, (x, y, 0.5), 18, 1.6, 3.0, 1.4, col, 0.04),
+            // claiming: a puff of dust
+            8 => self.burst(SMOKE, (x, y, 0.1), 2, 0.3, 0.2, 0.8, abgr(120, 60, 60), 0.12),
+            _ => {}
+        }
+    }
+
+    // advances projectiles (trails, impacts) and particles
+    pub(crate) fn update_particles(&mut self, dt: f32) {
+        // trails and impacts of the projectiles
+        let mut trails: Vec<(u8, (f32, f32, f32), f32)> = Vec::new();
+        let mut impacts: Vec<Fx> = Vec::new();
+        for f in self.fx.iter() {
+            if f.kind != 0 {
+                continue;
+            }
+            let p0 = f.t / f.max;
+            let p1 = (f.t + dt) / f.max;
+            if p0 < 1.0 {
+                trails.push((f.style, fx_pos(f, p1.min(1.0)), f.size));
+            }
+            if p0 < 1.0 && p1 >= 1.0 {
+                impacts.push(*f);
+            }
+        }
+        for (style, at, size) in trails {
+            let (rate, kind, col, psize, life) = match style {
+                ST_FIRE => (70.0, EMBER, abgr(255, 150, 40), 0.045, 0.9),
+                ST_SHADOW => (45.0, EMBER, abgr(200, 70, 255), 0.035, 1.0),
+                ST_HOLY => (35.0, MOTE, abgr(255, 240, 150), 0.03, 0.8),
+                ST_ARCANE => (40.0, EMBER, abgr(255, 170, 90), 0.03, 0.9),
+                ST_RUNE => (45.0, SPARK, abgr(90, 200, 255), 0.03, 0.7),
+                ST_MAGIC => (45.0, EMBER, abgr(255, 90, 220), 0.035, 0.9),
+                ST_CANNON => (30.0, SMOKE, abgr(70, 70, 76), 0.1, 0.9),
+                ST_ARROW | ST_ARROW_WALL => (0.0, EMBER, 0, 0.0, 0.0),
+                _ => (12.0, EMBER, abgr(180, 210, 230), 0.03, 0.6),
+            };
+            let n = rate * dt * size;
+            let mut count = n.floor() as usize;
+            if self.vrng.f() < n.fract() {
+                count += 1;
+            }
+            for _ in 0..count {
+                let v = (self.vrng.f() * 0.6 - 0.3, self.vrng.f() * 0.6 - 0.3, if kind == SMOKE { 0.3 } else { 0.2 });
+                let j = (self.vrng.f() * 0.06 - 0.03, self.vrng.f() * 0.06 - 0.03);
+                let m = life * (0.7 + 0.6 * self.vrng.f());
+                self.part(kind, (at.0 + j.0, at.1 + j.1, at.2), v, m, col, psize * size.sqrt());
+            }
+            if style == ST_FIRE && self.vrng.f() < 12.0 * dt {
+                self.part(SMOKE, at, (0.0, 0.0, 0.4), 1.2, abgr(60, 50, 50), 0.12);
+            }
+        }
+        for f in impacts {
+            self.impact(&f);
+        }
+        // particles
+        for p in self.parts.iter_mut() {
+            p.t += dt;
+            match p.kind {
+                SMOKE => {
+                    p.x += p.vx * dt;
+                    p.y += p.vy * dt;
+                    p.h += p.vh * dt;
+                    p.vx *= 1.0 - dt;
+                    p.vy *= 1.0 - dt;
+                    p.size += dt * 0.35;
+                }
+                MOTE => {
+                    p.x += p.vx * dt;
+                    p.y += p.vy * dt;
+                    p.h += p.vh * dt;
+                }
+                FLASH | RING => {}
+                _ => {
+                    // falling: embers drift down slower than sparks and debris
+                    let g = if p.kind == EMBER { GRAVITY * 0.35 } else { GRAVITY };
+                    p.vh -= g * dt;
+                    p.x += p.vx * dt;
+                    p.y += p.vy * dt;
+                    p.h += p.vh * dt;
+                    if p.h <= 0.02 {
+                        p.h = 0.02;
+                        if matches!(p.kind, SPARK | COIN) && p.vh < -1.0 {
+                            p.vh = -p.vh * 0.35;
+                            p.vx *= 0.5;
+                            p.vy *= 0.5;
+                        } else {
+                            p.vh = 0.0;
+                            p.vx *= 0.8;
+                            p.vy *= 0.8;
+                        }
+                    }
+                }
+            }
+        }
+        self.parts.retain(|p| p.t < p.max);
+        // stuck arrows fall out when their wall is dug away; everything fades in the end
+        let map = &self.map;
+        for p in self.stuck.iter_mut() {
+            p.t += dt;
+            if p.kind == ARROW && p.h > 0.1 {
+                let (tx, ty) = ((p.x + p.vx * 0.08) as i32, (p.y + p.vy * 0.08) as i32);
+                if !map.get(tx, ty).map_or(false, |t| t.solid()) {
+                    p.t = p.max;
+                }
+            }
+        }
+        self.stuck.retain(|p| p.t < p.max);
+    }
+
+    fn impact(&mut self, f: &Fx) {
+        let size = f.size;
+        let (x, y) = (f.x2, f.y2);
+        match f.style {
+            ST_FIRE => {
+                // the fireball explodes on the ground
+                let at = (x, y, 0.15);
+                self.part(FLASH, at, (0.0, 0.0, 0.0), 0.45, abgr(255, 170, 60), 0.9 * size);
+                self.part(RING, (x, y, 0.05), (0.0, 0.0, 0.0), 0.5, abgr(255, 120, 40), 1.4 * size);
+                self.burst(EMBER, at, (24.0 * size) as usize, 2.8 * size, 3.0, 1.2, abgr(255, 140, 40), 0.05);
+                self.burst(SPARK, at, 10, 3.5, 2.5, 0.7, abgr(255, 230, 120), 0.035);
+                self.burst(SMOKE, (x, y, 0.3), 8, 0.6, 0.7, 2.2, abgr(70, 60, 60), 0.22);
+                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 25.0, col: 0, size: 0.7 * size });
+            }
+            ST_CANNON => {
+                // the ball explodes: flash, stones and dirt flying, smoke
+                let at = (x, y, 0.2);
+                self.part(FLASH, at, (0.0, 0.0, 0.0), 0.3, abgr(255, 200, 120), 0.7 * size);
+                self.part(RING, (x, y, 0.05), (0.0, 0.0, 0.0), 0.4, abgr(220, 200, 170), 1.6);
+                self.burst(DEBRIS, at, 16, 3.0, 3.5, 1.6, abgr(84, 70, 64), 0.07);
+                self.burst(DEBRIS, at, 6, 2.5, 3.0, 1.4, abgr(120, 92, 70), 0.05);
+                self.burst(SPARK, at, 12, 4.0, 2.5, 0.6, abgr(255, 200, 100), 0.03);
+                self.burst(SMOKE, (x, y, 0.3), 10, 0.8, 0.6, 2.4, abgr(80, 80, 86), 0.25);
+                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 20.0, col: 0, size: 0.6 });
+            }
+            ST_ARROW | ST_ARROW_WALL => {
+                let (dx, dy) = (f.x2 - f.x, f.y2 - f.y);
+                let l = (dx * dx + dy * dy).sqrt().max(0.01);
+                let (dx, dy) = (dx / l, dy / l);
+                if f.style == ST_ARROW_WALL {
+                    self.burst(DEBRIS, (x, y, f.h2), 3, 0.8, 1.0, 0.8, abgr(110, 90, 80), 0.04);
+                    let h = f.h2 + self.vrng.f() * 0.2;
+                    self.stick(Part { kind: ARROW, x, y, h, vx: dx, vy: dy, vh: -0.08, t: 0.0, max: STUCK_LIFE, col: 0, size: 1.0 });
+                } else if self.vrng.f() < 0.35 {
+                    // glanced off: stuck in the floor next to the target
+                    let (ox, oy) = (self.vrng.f() * 0.7 - 0.35, self.vrng.f() * 0.7 - 0.35);
+                    let tilt = -0.6 - self.vrng.f() * 0.6;
+                    let n = (1.0 + tilt * tilt).sqrt();
+                    self.stick(Part { kind: ARROW, x: x + ox, y: y + oy, h: 0.04, vx: dx / n, vy: dy / n, vh: tilt / n, t: 0.0, max: STUCK_LIFE, col: 0, size: 1.0 });
+                }
+            }
+            ST_SHADOW => self.burst(EMBER, (x, y, f.h2), 14, 1.6, 1.5, 0.9, abgr(190, 70, 255), 0.04),
+            ST_HOLY => self.burst(MOTE, (x, y, f.h2), 12, 0.8, 0.8, 0.8, abgr(255, 240, 160), 0.035),
+            ST_ARCANE => self.burst(EMBER, (x, y, f.h2), 14, 1.8, 1.5, 0.8, abgr(255, 180, 100), 0.035),
+            ST_RUNE => {
+                self.burst(SPARK, (x, y, f.h2), 16, 2.5, 2.0, 0.7, abgr(110, 210, 255), 0.035);
+                self.part(FLASH, (x, y, f.h2), (0.0, 0.0, 0.0), 0.2, abgr(150, 220, 255), 0.4);
+            }
+            ST_MAGIC => self.burst(EMBER, (x, y, f.h2), 14, 1.8, 1.5, 0.9, abgr(255, 100, 220), 0.04),
+            _ => self.burst(SPARK, (x, y, f.h2), 6, 1.5, 1.2, 0.5, f.col, 0.03),
+        }
+    }
+
+    // the last projectile gets a style
+    pub(crate) fn style_last_fx(&mut self, style: u8) {
+        if let Some(f) = self.fx.last_mut() {
+            f.style = style;
+        }
+    }
+
+    // where an arrow flying from (x, y) along (dx, dy) ends: the first wall within `max`
+    pub(crate) fn arrow_end(&self, x: f32, y: f32, dx: f32, dy: f32, max: f32) -> (f32, f32, bool) {
+        let mut d = 0.0;
+        while d < max {
+            d += 0.1;
+            let (px, py) = (x + dx * d, y + dy * d);
+            if self.map.get(px as i32, py as i32).map_or(true, |t| t.solid()) {
+                let back = (d - 0.12).max(0.0);
+                return (x + dx * back, y + dy * back, true);
+            }
+        }
+        (x + dx * max, y + dy * max, false)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn projectiles_trail_and_explode_and_arrows_stick() {
+        let mut g = Game::new(3, 64, 64);
+        let (cx, cy) = g.map.core;
+        let (x, y) = (cx as f32 + 1.5, cy as f32 - 1.5);
+        g.shot(x, y, 0.5, x + 3.0, y, 0.45, 0.3, 0xffffffff);
+        g.style_last_fx(ST_FIRE);
+        let (ex, ey, wall) = g.arrow_end(x, y, -1.0, 0.0, 20.0);
+        assert!(wall);
+        g.shot(x, y, 0.5, ex, ey, 0.45, 0.3, 0xffffffff);
+        g.style_last_fx(ST_ARROW_WALL);
+        let mut trail = 0;
+        for _ in 0..4 {
+            g.update(0.05);
+            trail = trail.max(g.parts.len());
+        }
+        assert!(trail > 3, "fire trail: {}", trail);
+        for _ in 0..6 {
+            g.update(0.05);
+        }
+        assert!(g.parts.iter().any(|p| p.kind == FLASH) || g.stuck.iter().any(|p| p.kind == SCORCH), "explosion");
+        assert!(g.stuck.iter().any(|p| p.kind == ARROW), "arrow stuck");
+        // particles fall to the ground and vanish
+        for _ in 0..200 {
+            g.update(0.05);
+        }
+        assert!(g.parts.iter().all(|p| p.h >= 0.0));
+        assert!(g.parts.len() < 5);
+        assert!(g.stuck.iter().any(|p| p.kind == ARROW), "arrows stay for minutes");
+    }
+}

src/render3d.rs

@@ -1026,6 +1026,7 @@ impl R3d {
         draw_landmarks_solid(g, t);
         draw_towers_solid(g);
         crate::props::draw_props_solid(g, cam, t);
+        draw_parts_solid(g);
 
         // ---- unlit glow / overlays
         gl_use_material(&self.glow);
@@ -1062,6 +1063,7 @@ impl R3d {
         for f in &g.fx {
             draw_fx(f, t);
         }
+        draw_parts_glow(g);
         gl_use_default_material();
         crate::ui::begin_ui();
         if let (true, Some((rt, tw, th))) = (div > 1, self.target.as_ref()) {
@@ -2070,12 +2072,105 @@ fn draw_flag(f: usize, t: f32) {
     draw_mesh(&Mesh { vertices: v, indices: vec![0, 1, 2], texture: None });
 }
 
+// projectiles with a look of their own (styles in particles.rs)
+fn draw_projectile(f: &Fx, p: f32, t: f32) {
+    use crate::particles::*;
+    let at = |q: f32| {
+        let (x, y, h) = fx_pos(f, q);
+        vec3(x, h, y)
+    };
+    let head = at(p);
+    let c = rgba(f.col);
+    let sz = f.size;
+    match f.style {
+        ST_ARROW | ST_ARROW_WALL => {
+            let back = at((p - 0.08).max(0.0));
+            let dir = (head - back).normalize_or_zero();
+            line3(head - dir * 0.3, head, 0.03, Color::from_rgba(120, 84, 48, 255));
+            draw_cube(head, Vec3::splat(0.035), None, Color::from_rgba(200, 200, 210, 255));
+            draw_cube(head - dir * 0.28, Vec3::splat(0.05), None, Color::from_rgba(230, 230, 230, 255));
+        }
+        ST_CANNON => {
+            draw_sphere(head, 0.1 * sz, None, Color::from_rgba(24, 24, 28, 255));
+            draw_sphere(head, 0.14 * sz, None, Color::new(1.0, 0.6, 0.2, 0.15));
+        }
+        ST_FIRE => {
+            let flick = 1.0 + (t * 30.0 + f.x).sin() * 0.12;
+            draw_sphere(head, 0.08 * sz * flick, None, Color::new(1.0, 0.95, 0.6, 1.0));
+            draw_sphere(head, 0.14 * sz * flick, None, Color::new(1.0, 0.55, 0.12, 0.8));
+            draw_sphere(head, 0.24 * sz * flick, None, Color::new(1.0, 0.3, 0.05, 0.25));
+        }
+        _ => {
+            let tail = at((p - 0.3).max(0.0));
+            line3(tail, head, 0.06 * sz, Color::new(c.r, c.g, c.b, 0.7));
+            draw_sphere(head, 0.08 * sz, None, c);
+            draw_sphere(head, 0.17 * sz, None, Color::new(c.r, c.g, c.b, 0.25));
+        }
+    }
+}
+
+// particles that glow (embers, sparks, smoke, flashes, shock waves)
+fn draw_parts_glow(g: &Game) {
+    use crate::particles::*;
+    for p in &g.parts {
+        let c = rgba(p.col);
+        let life = (p.t / p.max).clamp(0.0, 1.0);
+        let at = vec3(p.x, p.h, p.y);
+        match p.kind {
+            EMBER | SPARK | MOTE => {
+                let s = p.size * (1.0 - life * 0.6);
+                draw_cube(at, Vec3::splat(s), None, Color::new(c.r, c.g, c.b, 1.0 - life * life));
+            }
+            SMOKE => draw_sphere(at, p.size, None, Color::new(c.r, c.g, c.b, 0.35 * (1.0 - life))),
+            FLASH => {
+                let r = p.size * (0.3 + life * 0.9);
+                draw_sphere(at, r * 0.6, None, Color::new(1.0, 0.95, 0.75, 1.0 - life));
+                draw_sphere(at, r, None, Color::new(c.r, c.g, c.b, 0.6 * (1.0 - life)));
+            }
+            RING => ring(at, p.size * (0.2 + life), Color::new(c.r, c.g, c.b, 0.8 * (1.0 - life))),
+            _ => {}
+        }
+    }
+    // scorch marks on the floor
+    for p in g.stuck.iter().filter(|p| p.kind == SCORCH) {
+        let fade = 1.0 - (p.t / p.max).clamp(0.0, 1.0);
+        disc(vec3(p.x, 0.015, p.y), p.size, Color::new(0.03, 0.02, 0.02, 0.55 * fade), 14);
+    }
+}
+
+// solid particles: debris, coins and the arrows stuck in walls and floors
+fn draw_parts_solid(g: &Game) {
+    use crate::particles::*;
+    for p in &g.parts {
+        let c = rgba(p.col);
+        let at = vec3(p.x, p.h, p.y);
+        match p.kind {
+            DEBRIS | COIN => {
+                let life = (p.t / p.max).clamp(0.0, 1.0);
+                let s = p.size * if life > 0.75 { (1.0 - life) * 4.0 } else { 1.0 };
+                draw_cube(at, vec3(s, if p.kind == COIN { s * 0.4 } else { s }, s), None, c);
+            }
+            _ => {}
+        }
+    }
+    for p in g.stuck.iter().filter(|p| p.kind == ARROW) {
+        let left = p.max - p.t;
+        let k = if left < 10.0 { left / 10.0 } else { 1.0 };
+        let tip = vec3(p.x, p.h, p.y);
+        let dir = vec3(p.vx, p.vh, p.vy).normalize_or_zero();
+        let tail = tip - dir * (0.32 * k);
+        line3(tail, tip + dir * 0.03, 0.03, Color::from_rgba(116, 80, 46, 255));
+        draw_cube(tail, vec3(0.05, 0.05, 0.05) * k, None, Color::from_rgba(226, 226, 226, 255));
+    }
+}
+
 fn draw_fx(f: &Fx, t: f32) {
     let p = (f.t / f.max).clamp(0.0, 1.0);
     let c = rgba(f.col);
     let a = |alpha: f32| Color::new(c.r, c.g, c.b, alpha);
     let at = vec3(f.x, f.h, f.y);
     match f.kind {
+        0 if f.style != crate::particles::ST_PLAIN => draw_projectile(f, p, t),
         0 => {
             let from = vec3(f.x, f.h, f.y);
             let to = vec3(f.x2, f.h2, f.y2);