From d6acee5a66092f745224d0e4d0fd87e48c9b67c5 Mon Sep 17 00:00:00 2001
From: Noah Petherbridge <root@kirsle.net>
Date: Thu, 7 Oct 2021 18:49:09 -0700
Subject: [PATCH] Adjust Gravity and Prevent Moonwalking

* Tweak max gravity speed to match player max velocity.
* Boy's script watches for his velocity to flip suddenly and stops
  animations, limiting the moonwalking a bit.
* JS API: Self.GetVelocity() added.
---
 dev-assets/doodads/boy/boy.js | 12 ++++++++++--
 pkg/balance/numbers.go        |  2 +-
 pkg/play_scene_touch.go       |  3 ++-
 pkg/uix/scripting.go          |  1 +
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/dev-assets/doodads/boy/boy.js b/dev-assets/doodads/boy/boy.js
index 02f877b..8c9f532 100644
--- a/dev-assets/doodads/boy/boy.js
+++ b/dev-assets/doodads/boy/boy.js
@@ -1,11 +1,9 @@
 function main() {
 	var playerSpeed = 12;
-	var gravity = 4;
 	var Vx = Vy = 0;
 
 	var animating = false;
 	var animStart = animEnd = 0;
-	var animFrame = animStart;
 
 	Self.SetMobile(true);
 	Self.SetInventory(true);
@@ -14,10 +12,20 @@ function main() {
 	Self.AddAnimation("walk-left", 200, ["stand-left", "walk-left-1", "walk-left-2", "walk-left-3", "walk-left-2", "walk-left-1"]);
 	Self.AddAnimation("walk-right", 200, ["stand-right", "walk-right-1", "walk-right-2", "walk-right-3", "walk-right-2", "walk-right-1"]);
 
+	// If the player suddenly changes direction, reset the animation state to quickly switch over.
+	var lastVelocity = Vector(0, 0);
+
 	Events.OnKeypress(function (ev) {
 		Vx = 0;
 		Vy = 0;
 
+		var curVelocity = Self.GetVelocity();
+		if ((lastVelocity.X < 0 && curVelocity.X > 0) ||
+			(lastVelocity.X > 0 && curVelocity.X < 0)) {
+			Self.StopAnimation();
+		}
+		lastVelocity = curVelocity;
+
 		if (ev.Right) {
 			if (!Self.IsAnimating()) {
 				Self.PlayAnimation("walk-right", null);
diff --git a/pkg/balance/numbers.go b/pkg/balance/numbers.go
index b63abbe..6e0aa83 100644
--- a/pkg/balance/numbers.go
+++ b/pkg/balance/numbers.go
@@ -26,7 +26,7 @@ var (
 	PlayerMaxVelocity   float64 = 7
 	PlayerJumpVelocity  float64 = -20
 	PlayerAcceleration  float64 = 0.12
-	Gravity             float64 = 6
+	Gravity             float64 = 7
 	GravityAcceleration float64 = 0.1
 	SlopeMaxHeight              = 8 // max pixel height for player to walk up a slope
 
diff --git a/pkg/play_scene_touch.go b/pkg/play_scene_touch.go
index c9cf933..93a5248 100644
--- a/pkg/play_scene_touch.go
+++ b/pkg/play_scene_touch.go
@@ -31,7 +31,8 @@ func (s *PlayScene) LoopTouchable(ev *event.State) {
 	// Idle means that they are not holding any directional or otherwise input key.
 	// Keyboard inputs and touch events from this function will set these keys.
 	// See if it stays unset long enough to consider idle.
-	if !ev.Up && !ev.Down && !ev.Right && !ev.Left && !ev.Space {
+	var isGrounded = (s.Player.HasGravity() && s.Player.Grounded()) || !s.Player.HasGravity()
+	if !ev.Up && !ev.Down && !ev.Right && !ev.Left && !ev.Space && isGrounded {
 		if s.idleLastStart.IsZero() {
 			s.idleLastStart = time.Now()
 		} else if time.Since(s.idleLastStart) > balance.PlayModeIdleTimeout {
diff --git a/pkg/uix/scripting.go b/pkg/uix/scripting.go
index 3ca4daf..b093d56 100644
--- a/pkg/uix/scripting.go
+++ b/pkg/uix/scripting.go
@@ -26,6 +26,7 @@ func (w *Canvas) MakeSelfAPI(actor *Actor) map[string]interface{} {
 		"SetHitbox":      actor.SetHitbox,
 		"Hitbox":         actor.Hitbox,
 		"SetVelocity":    actor.SetVelocity,
+		"GetVelocity":    actor.Velocity,
 		"SetMobile":      actor.SetMobile,
 		"SetInventory":   actor.SetInventory,
 		"HasInventory":   actor.HasInventory,