Place masses with random velocity, add crosshairs in the center of the screen

Author: Heliodex

fw/game/game.go

@@ -3,6 +3,7 @@ package game
 import (
 	"fw/util"
 	"math"
+	"math/rand/v2"
 	"runtime"
 	"strconv"
 	"time"
@@ -103,11 +104,17 @@ var (
 	trace     []State
 	toggleAdd = &Toggle{
 		onPress: func() {
+			colours := []util.Pixel{util.Red, util.Green, util.Blue, util.White, util.Yellow, util.Cyan, util.Magenta, util.Grey2, util.Grey3}
+			c := colours[len(sim.masses)%len(colours)]
+
+			// centre on window crosshairs
+			centre := util.V2[float64](util.Width/2, util.Height/2).Sub(sim.origin.Float64()).Div(sim.scale)
+
 			newmass := Mass{
-				mass:     1,
-				position: util.V2((float64(f%20)-10)*0.1, (float64((f/20)%20)-10)*0.1),
-				velocity: util.V2[float64](0, 0),
-				colour:   util.White,
+				mass:     rand.Float64()*1.5 + 0.5,
+				position: centre,
+				velocity: util.V2(rand.Float64()*2-1, rand.Float64()*2-1).Mul(0.3),
+				colour:   c,
 			}
 			sim.masses = append(sim.masses, newmass)
 		},
@@ -122,21 +129,28 @@ var (
 	}
 )
 
+const (
+	hOffset = 15
+	vOffset = 18
+)
+
+var Texts = [util.ButtonsCount]*Text{
+	{FontDex, "W", util.V2(2+hOffset-2, 2), util.Red},
+	{FontDex, "A", util.V2(2, 2+vOffset), util.Red},
+	{FontDex, "S", util.V2(2+hOffset, 2+vOffset*2), util.Red},
+	{FontDex, "D", util.V2(2+hOffset*2, 2+vOffset), util.Red},
+	{FontDex, "I", util.V2(2+util.Width-hOffset*2, 2), util.Red},
+	{FontDex, "J", util.V2(2+util.Width-hOffset*3, 2+vOffset), util.Red},
+	{FontDex, "K", util.V2(2+util.Width-hOffset*2, 2+vOffset*2), util.Red},
+	{FontDex, "L", util.V2(2+util.Width-hOffset, 2+vOffset), util.Red},
+}
+
+var Crosshairs = &Crosshair{util.V2(util.Width/2, util.Height/2), util.Grey3, 3}
+
 // ran every frame (or, more like this is what makes the frames)
 func Update(en util.Engine) {
 	btns := en.Buttons()
 
-	Texts := [util.ButtonsCount]*Text{
-		{FontDex, "W", util.V2(2+20-2, 2), util.Red},
-		{FontDex, "A", util.V2(2, 26), util.Red},
-		{FontDex, "S", util.V2(2+20, 50), util.Red},
-		{FontDex, "D", util.V2(2+40, 26), util.Red},
-		{FontDex, "I", util.V2(109+20+1, 2), util.Red},
-		{FontDex, "J", util.V2(109, 26), util.Red},
-		{FontDex, "K", util.V2(109+20, 50), util.Red},
-		{FontDex, "L", util.V2(109+40, 26), util.Red},
-	}
-
 	// read button states
 	for i, b := range btns {
 		if b.Pressed() {
@@ -146,8 +160,29 @@ func Update(en util.Engine) {
 		}
 	}
 
-	toggleAdd.Update(btns[3].Pressed())
-	toggleRemove.Update(btns[1].Pressed())
+	if btns[4].Pressed() {
+		sim.dt += 0.001
+	}
+
+	if btns[6].Pressed() {
+		sim.dt -= 0.001
+	}
+
+	if btns[2].Pressed() {
+		sim.origin = sim.origin.Add(util.V2(0, -2))
+	}
+	if btns[0].Pressed() {
+		sim.origin = sim.origin.Add(util.V2(0, 2))
+	}
+	if btns[1].Pressed() {
+		sim.origin = sim.origin.Add(util.V2(2, 0))
+	}
+	if btns[3].Pressed() {
+		sim.origin = sim.origin.Add(util.V2(-2, 0))
+	}
+
+	toggleAdd.Update(btns[7].Pressed())
+	toggleRemove.Update(btns[5].Pressed())
 
 	// update simulation
 	forces := make([]util.Vector2[float64], len(sim.masses))
@@ -205,6 +240,8 @@ func Update(en util.Engine) {
 		e.drawTo(en.ScreenBuffer())
 	}
 
+	Crosshairs.drawTo(en.ScreenBuffer())
+
 	en.Render()
 	f++
 }

fw/game/tools.go

@@ -77,6 +77,18 @@ func abs(x int) int {
 	return x
 }
 
+func drawVLine(buf *util.ScreenBuffer, x, y1, y2 int, colour util.Pixel) {
+	for y := y1; y <= y2; y++ {
+		buf.Set(x, y, colour)
+	}
+}
+
+func drawHLine(buf *util.ScreenBuffer, y, x1, x2 int, colour util.Pixel) {
+	for x := x1; x <= x2; x++ {
+		buf.Set(x, y, colour)
+	}
+}
+
 func drawLine(buf *util.ScreenBuffer, p1, p2 util.Vector2[int], colour util.Pixel) {
 	dx := abs(p2.X - p1.X)
 	dy := -abs(p2.Y - p1.Y)
@@ -468,3 +480,13 @@ type Mass struct {
 	colour             util.Pixel
 }
 
+type Crosshair struct {
+	pos    util.Vector2[int]
+	colour util.Pixel
+	size   int
+}
+
+func (c *Crosshair) drawTo(buf *util.ScreenBuffer) {
+	drawHLine(buf, c.pos.Y, c.pos.X-c.size, c.pos.X+c.size, c.colour)
+	drawVLine(buf, c.pos.X, c.pos.Y-c.size, c.pos.Y+c.size, c.colour)
+}

fw/util/util.go

@@ -72,6 +72,7 @@ var (
 
 	Grey1 = MakePixel(0x20, 0x20, 0x20)
 	Grey2 = MakePixel(0x40, 0x40, 0x40)
+	Grey3 = MakePixel(0x80, 0x80, 0x80)
 )
 
 type buttonId uint8
@@ -141,6 +142,10 @@ func (v Vector2[T]) Div(scalar float64) Vector2[T] {
 	return Vector2[T]{X: T(float64(v.X) / scalar), Y: T(float64(v.Y) / scalar)}
 }
 
+func (v Vector2[T]) Neg() Vector2[T] {
+	return Vector2[T]{X: -v.X, Y: -v.Y}
+}
+
 func (v Vector2[T]) Len() T {
 	x2 := v.X * v.X
 	y2 := v.Y * v.Y
@@ -150,3 +155,7 @@ func (v Vector2[T]) Len() T {
 func (v Vector2[float64]) Int() Vector2[int] {
 	return V2(int(v.X), int(v.Y))
 }
+
+func (v Vector2[int]) Float64() Vector2[float64] {
+	return V2(float64(v.X), float64(v.Y))
+}