loading/updater.go

package main

import (
	"loading/objects"
	"math"

	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/inpututil"
)

// Update proceeds the game state.
// Update is called every tick (1/60 [s] by default).
func (g *Game) Update() error {
	// Write your game's logical update.
	g.counter++

	g.UpdatePlayer()
	//g.UpdateEnemies()
	g.UpdateBobbles()

	return nil
}

func (g *Game) UpdateBobbles() {

	for i := 0; i < len(g.bobbles); i++ {
		bobby := &g.bobbles[i]
		bobby.Radius = objects.GetDefaultRadius() + float32(10*math.Sin(float64(g.counter)/(math.Pi*4)))
	}

}

func (g *Game) UpdatePlayer() {

	//update player angle based on mouse position
	mx, my := ebiten.CursorPosition()
	playerAngle := float32(math.Atan2(float64(float32(my)-g.player.Pose.Y), float64(float32(mx)-g.player.Pose.X)))
	g.player.Angle = playerAngle

	//update position based on wasd input
	g.keys = inpututil.AppendPressedKeys(g.keys[:0])
	step := float32(10)
	for _, k := range g.keys {
		switch k {
		case ebiten.KeyW:
			g.player.Pose.Y = g.player.Pose.Y - step
		case ebiten.KeyA:
			g.player.Pose.X = g.player.Pose.X - step
		case ebiten.KeyS:
			g.player.Pose.Y = g.player.Pose.Y + step
		case ebiten.KeyD:
			g.player.Pose.X = g.player.Pose.X + step
		default:
		}
	}

}

func (g *Game) UpdateEnemies() {
	/*
		we're going to rotate the enemies so they slowly face the player, to do this we'll find the angle delta
		between the player and the enemy via atan2, then add approximately one quarter of this value to the
		current enemy angle
	*/
	/*
		for _, e := range g.enemies {
			//diff := float32(math.Atan2(float64(g.player.Pose.Y-e.Pose.Y), float64(g.player.Pose.X-e.Pose.X)))
			e.Angle = e.Angle + math.Pi/4
		}
	*/

	for i := 0; i < len(g.enemies); i++ {
		enemy := &g.enemies[i]

		//find distancees between enemy and player
		dx := float64(g.player.Pose.X - enemy.Pose.X)
		dy := float64(g.player.Pose.Y - enemy.Pose.Y)

		//current sign
		currentSign := enemy.DeltaAngle / float32(math.Abs(float64(enemy.DeltaAngle)))

		targetAngle := float32(math.Atan2(dy, dx)) + math.Pi*2

		//_, absTargetAngle := math.Modf(float64(targetAngle))

		phi := float32(math.Mod(float64(targetAngle-enemy.Angle), float64(2*math.Pi)))
		if phi > math.Pi {
			enemy.DeltaAngle = math.Pi - phi
		} else {
			enemy.DeltaAngle = phi
		}

		//enemy.DeltaAngle = float32(math.Min(2*math.Pi-math.Abs(float64(enemy.Angle-targetAngle)), math.Abs(float64(enemy.Angle-targetAngle))))

		enemy.Angle = enemy.Angle + enemy.DeltaAngle/16

		enemy.SignFlip = currentSign

		for j := 0; j < len(g.enemies); j++ {
			if j == i {
				continue
			}

			xdist := (g.enemies[j].Pose.X - enemy.Pose.X)
			ydist := (g.enemies[j].Pose.Y - enemy.Pose.Y)

			//quick boundary check before we get to the algebra
			if xdist > enemy.Buffer || ydist > enemy.Buffer {
				continue
			}

			dist := float32(math.Sqrt(float64(xdist*xdist + ydist*ydist)))
			if dist < enemy.Buffer {
				enemy.Pose.X = enemy.Pose.X + dist*float32(math.Cos(float64(targetAngle)))
				enemy.Pose.Y = enemy.Pose.Y + dist*float32(math.Sin(float64(targetAngle)))
			}

		}

		enemy.Pose.X = enemy.Pose.X + float32(dx)/360
		enemy.Pose.Y = enemy.Pose.Y + float32(dy)/360

		//enemy.Angle = enemy.Angle + enemy.DeltaAngle/(math.Pi/4)
	}

}