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August 4, 2025 17:57
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Parallax starfield effect implemented using text mode terminal interface with tcell.
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| package main | |
| import ( | |
| "fmt" | |
| "math" | |
| "math/rand" | |
| "os" | |
| "time" | |
| "github.com/gdamore/tcell/v2" | |
| ) | |
| // Star represents a star with position, depth, and velocity | |
| type Star struct { | |
| x, y float64 // Current position | |
| dx, dy float64 // Velocity (based on angle and depth) | |
| depth float64 // 0.1 (close, fast) to 1.0 (far, slow) | |
| symbol rune // '*', '+', or '.' based on depth | |
| } | |
| // Screensaver manages the starfield | |
| type Screensaver struct { | |
| screen tcell.Screen | |
| stars []Star | |
| numStars int | |
| width, height int | |
| } | |
| // NewScreensaver initializes the screensaver | |
| func NewScreensaver() (*Screensaver, error) { | |
| s, err := tcell.NewScreen() | |
| if err != nil { | |
| return nil, err | |
| } | |
| if err := s.Init(); err != nil { | |
| return nil, err | |
| } | |
| w, h := s.Size() | |
| return &Screensaver{ | |
| screen: s, | |
| numStars: 250, | |
| stars: make([]Star, 250), | |
| width: w, | |
| height: h, | |
| }, nil | |
| } | |
| // initStar initializes a star at a random position in the center rectangle with outward velocity | |
| func (s *Screensaver) initStar() Star { | |
| centerX, centerY := float64(s.width)/2, float64(s.height)/2 | |
| rectW := math.Max(2, float64(s.width)*0.2) | |
| rectH := math.Max(2, float64(s.height)*0.3) | |
| rectLeft := centerX - rectW/2 | |
| rectTop := centerY - rectH/2 | |
| x := rectLeft + rand.Float64()*rectW | |
| y := rectTop + rand.Float64()*rectH | |
| dx := x - centerX | |
| dy := y - centerY | |
| if dx == 0 && dy == 0 { | |
| dx = rand.Float64() - 0.5 | |
| dy = rand.Float64() - 0.5 | |
| } | |
| norm := math.Hypot(dx, dy) | |
| dx /= norm | |
| dy /= norm | |
| depth := 0.1 + rand.Float64()*0.9 | |
| speed := 0.25 / depth | |
| return Star{ | |
| x: x, | |
| y: y, | |
| dx: dx * speed, | |
| dy: dy * speed, | |
| depth: depth, | |
| symbol: getSymbol(depth), | |
| } | |
| } | |
| // InitStars populates initial star positions at center | |
| func (s *Screensaver) InitStars() { | |
| for i := 0; i < s.numStars; i++ { | |
| s.stars[i] = s.initStar() | |
| } | |
| } | |
| // getSymbol assigns '*' (close), '+' (mid), or '.' (far) based on depth | |
| func getSymbol(depth float64) rune { | |
| if depth < 0.4 { | |
| return '*' | |
| } else if depth < 0.7 { | |
| return '+' | |
| } | |
| return '.' | |
| } | |
| // Draw renders the starfield | |
| func (s *Screensaver) Draw() { | |
| s.screen.Clear() | |
| for _, star := range s.stars { | |
| if star.x >= 0 && star.x < float64(s.width) && star.y >= 0 && star.y < float64(s.height) { | |
| s.screen.SetContent(int(star.x), int(star.y), star.symbol, nil, tcell.StyleDefault.Foreground(tcell.ColorWhite)) | |
| } | |
| } | |
| // Print current terminal size at the top left | |
| sizeStr := fmt.Sprintf("%dx%d", s.width, s.height) | |
| for i, r := range sizeStr { | |
| s.screen.SetContent(i+2, 1, r, nil, tcell.StyleDefault.Foreground(tcell.ColorWhite)) | |
| } | |
| s.screen.Show() | |
| } | |
| // Update moves stars and checks inactivity | |
| func (s *Screensaver) Update() { | |
| for i := 0; i < s.numStars; i++ { | |
| s.stars[i].x += s.stars[i].dx | |
| s.stars[i].y += s.stars[i].dy | |
| // Respawn at center rectangle if star leaves screen | |
| if s.stars[i].x < 0 || s.stars[i].x >= float64(s.width) || s.stars[i].y < 0 || s.stars[i].y >= float64(s.height) { | |
| s.stars[i] = s.initStar() | |
| } | |
| } | |
| } | |
| // Run handles the main loop | |
| func (s *Screensaver) Run() { | |
| rand.Seed(time.Now().UnixNano()) | |
| for { | |
| s.Update() | |
| s.Draw() | |
| // Non-blocking event polling | |
| for s.screen.HasPendingEvent() { | |
| ev := s.screen.PollEvent() | |
| if ev == nil { | |
| break | |
| } | |
| switch tev := ev.(type) { | |
| case *tcell.EventKey: | |
| if tev.Key() == tcell.KeyCtrlC { | |
| return | |
| } | |
| case *tcell.EventResize: | |
| w, h := s.screen.Size() | |
| s.width, s.height = w, h | |
| } | |
| } | |
| time.Sleep(time.Second / 60) // 20 FPS | |
| } | |
| } | |
| func main() { | |
| s, err := NewScreensaver() | |
| if err != nil { | |
| // Print error to stderr and exit | |
| println("Failed to initialize screensaver:", err.Error()) | |
| os.Exit(1) | |
| } | |
| s.InitStars() | |
| defer s.screen.Fini() | |
| s.Run() | |
| } |
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