Game Feel & Polish for Nethercore ZX

Game feel ("juice") transforms functional mechanics into satisfying experiences. All code MUST be deterministic for rollback netcode.

Core Principles

Principle	Implementation
Exaggeration	Screen shake, scale bounces, speed lines
Anticipation	Wind-up animations, audio cues before action
Follow-through	Lingering effects after action ends
Immediate feedback	Visual + audio response within 1-2 frames

Screen Shake

struct ScreenShake {
    intensity: f32,
    duration: u32,
    remaining: u32,
}

impl ScreenShake {
    fn trigger(&mut self, intensity: f32, duration: u32) {
        self.intensity = intensity;
        self.duration = duration;
        self.remaining = duration;
    }

    fn update(&mut self) -> (f32, f32) {
        if self.remaining == 0 { return (0.0, 0.0); }

        let t = self.remaining as f32 / self.duration as f32;
        let current = self.intensity * t;
        let offset_x = (random() * 2.0 - 1.0) * current;
        let offset_y = (random() * 2.0 - 1.0) * current;

        self.remaining -= 1;
        (offset_x, offset_y)
    }
}

Shake Intensity Guide

Event	Intensity	Duration
Light hit	2-4 px	4-6 ticks
Heavy hit	6-10 px	8-12 ticks
Explosion	12-20 px	15-25 ticks
Boss attack	15-25 px	20-30 ticks

Hit Pause (Freeze Frames)

Momentary freeze on impact adds weight:

struct HitPause { remaining: u32 }

impl HitPause {
    fn trigger(&mut self, frames: u32) {
        self.remaining = self.remaining.max(frames);
    }

    fn is_paused(&self) -> bool { self.remaining > 0 }

    fn update(&mut self) {
        if self.remaining > 0 { self.remaining -= 1; }
    }
}

fn update(game: &mut Game) {
    game.hit_pause.update();
    if game.hit_pause.is_paused() { return; }  // Skip gameplay
    // Normal update...
}

Hit Pause Guide

Event	Duration
Light hit	2-3 frames
Heavy hit	4-6 frames
Critical	8-10 frames
Boss stagger	12-15 frames

Visual Feedback

Flash on Hit

fn render_entity(e: &Entity) {
    if e.flash_timer > 0 {
        material_emissive(0xFFFFFFFF);  // White flash
    }
    draw_mesh(e.mesh);
    material_emissive(0x000000FF);  // Reset
}

Scale Bounce

fn update_bounce(scale: &mut f32, target: f32, velocity: &mut f32) {
    let diff = target - *scale;
    *velocity += diff * 0.3;  // Spring force
    *velocity *= 0.8;  // Damping
    *scale += *velocity;
}

Audio Feedback

Event	Sound Type	Timing
Button press	UI click	Immediate
Jump	Whoosh	On input
Land	Thud	On contact
Hit	Impact + voice	On collision

fn on_hit(damage: i32) {
    play_sound(SOUND_HIT);
    if damage > 20 {
        play_sound(SOUND_HEAVY_HIT);
    }
}

Particle Hints

For particle effects (dust, sparks, debris):

// Spawn burst on landing
if just_landed {
    for _ in 0..5 {
        spawn_particle(Particle {
            pos: player_pos,
            vel: (random() * 2.0 - 1.0, random() * 0.5),
            life: 15,
            color: 0x888888FF,
        });
    }
}

Game Feel & Polish