151 lines
3.6 KiB
Go
151 lines
3.6 KiB
Go
package game
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import (
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"encoding/gob"
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"image"
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"math"
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"drjosh.dev/gurgle/engine"
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"github.com/hajimehoshi/ebiten/v2"
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"github.com/hajimehoshi/ebiten/v2/inpututil"
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)
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func init() {
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gob.Register(Awakeman{})
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}
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type Awakeman struct {
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engine.Sprite
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CameraID string
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camera *engine.Camera
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vx, vy float64
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facingLeft bool
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coyoteTimer int
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noclip bool
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animIdleLeft, animIdleRight, animRunLeft, animRunRight *engine.Anim
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}
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func (aw *Awakeman) Update() error {
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// TODO: better cheat for noclip
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if inpututil.IsKeyJustPressed(ebiten.KeyN) {
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aw.noclip = !aw.noclip
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}
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upd := aw.realUpdate
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if aw.noclip {
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upd = aw.noclipUpdate
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}
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if err := upd(); err != nil {
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return err
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}
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aw.camera.Zoom = 1
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if ebiten.IsKeyPressed(ebiten.KeyShift) {
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aw.camera.Zoom = 2
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}
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aw.camera.Centre = aw.Pos.Add(aw.Size.Div(2))
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return nil
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}
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func (aw *Awakeman) noclipUpdate() error {
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if ebiten.IsKeyPressed(ebiten.KeyUp) {
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aw.Pos.Y--
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}
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if ebiten.IsKeyPressed(ebiten.KeyDown) {
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aw.Pos.Y++
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}
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if ebiten.IsKeyPressed(ebiten.KeyLeft) {
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aw.Pos.X--
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}
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if ebiten.IsKeyPressed(ebiten.KeyRight) {
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aw.Pos.X++
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}
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return nil
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}
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func (aw *Awakeman) realUpdate() error {
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const (
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ε = 0.2
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restitution = -0.3
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gravity = 0.3
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airResistance = -0.01 // ⇒ terminal velocity = 30
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jumpVelocity = -4.2
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runVelocity = 1.4
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coyoteTime = 5
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)
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// High-school physics time! Under constant acceleration:
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// v = v_0 + a*t
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// and
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// s = t * (v_0 + v) / 2
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// (note t is in ticks and s is in world units)
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// and since we get one Update per tick (t = 1),
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// v = v_0 + a,
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// and
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// s = (v_0 + v) / 2.
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// Capture current v_0 to use later.
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ux, uy := aw.vx, aw.vy
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// Has traction?
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if aw.CollidesAt(aw.Pos.Add(image.Pt(0, 1))) {
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// Not falling.
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// Instantly decelerate (AW absorbs all kinetic E in legs, or something)
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aw.vy = 0
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aw.coyoteTimer = coyoteTime
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} else {
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// Falling. v = v_0 + a, and a = gravity + airResistance(v_0)
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aw.vy += gravity + airResistance*aw.vy
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if aw.coyoteTimer > 0 {
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aw.coyoteTimer--
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}
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}
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// Handle controls
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// NB: spacebar sometimes does things on web pages (scrolls down)
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if aw.coyoteTimer > 0 && (inpututil.IsKeyJustPressed(ebiten.KeySpace) || inpututil.IsKeyJustPressed(ebiten.KeyZ)) {
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// Jump. One frame of a = jumpVelocity (ignoring any gravity already applied this tick).
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aw.vy = jumpVelocity
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}
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switch {
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case ebiten.IsKeyPressed(ebiten.KeyLeft) || ebiten.IsKeyPressed(ebiten.KeyA):
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aw.vx = -runVelocity
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aw.SetAnim(aw.animRunLeft)
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aw.facingLeft = true
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case ebiten.IsKeyPressed(ebiten.KeyRight) || ebiten.IsKeyPressed(ebiten.KeyD):
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aw.vx = runVelocity
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aw.SetAnim(aw.animRunRight)
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aw.facingLeft = false
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default:
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aw.vx = 0
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aw.SetAnim(aw.animIdleRight)
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if aw.facingLeft {
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aw.SetAnim(aw.animIdleLeft)
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}
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}
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// s = (v_0 + v) / 2.
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aw.MoveX((ux+aw.vx)/2, nil)
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// For Y, on collision, bounce a little bit.
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// Does not apply to X because controls override it anyway.
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aw.MoveY((uy+aw.vy)/2, func() {
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aw.vy *= restitution
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if math.Abs(aw.vy) < ε {
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aw.vy = 0
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}
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})
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// aw.Pos is top-left corner, so add half size to get centre
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return aw.Sprite.Update()
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}
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func (aw *Awakeman) Prepare(game *engine.Game) {
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aw.camera = game.Component(aw.CameraID).(*engine.Camera)
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aw.animIdleLeft = &engine.Anim{Def: engine.AnimDefs["aw_idle_left"]}
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aw.animIdleRight = &engine.Anim{Def: engine.AnimDefs["aw_idle_right"]}
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aw.animRunLeft = &engine.Anim{Def: engine.AnimDefs["aw_run_left"]}
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aw.animRunRight = &engine.Anim{Def: engine.AnimDefs["aw_run_right"]}
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}
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func (aw *Awakeman) Scan() []interface{} { return []interface{}{&aw.Sprite} }
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