Codelaby

import SwiftUI

struct ContentView: View {
    @State private var start = Date.now
    
    var body: some View {
        VStack {
            TimelineView(.animation) { timeline in
                let time = start.distance(to: timeline.date)
                Rectangle()

Codelaby

import SwiftUI
import MetalKit

struct Particle {
  let color: SIMD4<Float>
  let radius: Float
  let lifespan: Float
  let position: SIMD2<Float>
  let velocity: SIMD2<Float>
}