Adjusted the way pieces are rotated when hovered.

Instead of changing the angular velocity to position the piece (which
causes issues when flipping pieces at weird angles, due to the variable
using euler angles), now the basis is set directly every physics frame
using Basis.slerp().

Also fixed spamming the flip button causing the basis to become the wrong
value. This was because the new hover_basis was based on the current
transform, not the current hover_basis.

This commit fixes #133.

game/Scripts/Game/Pieces/Piece.gd

@@ -27,15 +27,15 @@ class_name Piece
 signal client_set_hover_position(piece)
 signal scale_changed()
 
-const ANGULAR_FORCE_SCALAR = 25.0
 const HARMONIC_DAMPENING = 0.5
 const HELL_HEIGHT = -50.0
 const HOVER_INACTIVE_DURATION = 5.0
 const LINEAR_FORCE_SCALAR = 50.0
 const ROTATION_LOCK_AT = 0.001
+const ROTATION_SLERP_ALPHA = 0.5
 const SHAKING_THRESHOLD = 1000.0
-const TRANSFORM_LERP_ALPHA = 0.9
 const SHAKE_WAIT_DURATION = 500
+const TRANSFORM_LERP_ALPHA = 0.9
 
 export(NodePath) var effect_player_path: String
 
@@ -252,7 +252,7 @@ func play_effect(sound: AudioStream) -> void:
 
 # If you are hovering this piece, ask the server to flip the piece vertically.
 master func request_flip_vertically() -> void:
-	request_set_hover_basis(hover_basis.rotated(transform.basis.z, PI))
+	request_set_hover_basis(hover_basis.rotated(hover_basis.z, PI))
 
 # Request the server to apply an impulse to the piece.
 # position: The position to apply the impulse, relative to the piece's origin.
@@ -403,7 +403,10 @@ remotesync func set_hover_basis(new_hover_basis: Basis) -> void:
 	if get_tree().get_rpc_sender_id() != 1:
 		return
 
-	hover_basis = new_hover_basis
+	if new_hover_basis.is_equal_approx(Basis(Vector3.ZERO, Vector3.ZERO, Vector3.ZERO)):
+		return
+
+	hover_basis = new_hover_basis.orthonormalized()
 	sleeping = false
 
 # Set the hover position of the piece.
@@ -586,11 +589,12 @@ func _apply_hover_to_state(state: PhysicsDirectBodyState) -> void:
 	state.linear_velocity = LINEAR_FORCE_SCALAR * linear_dir
 
 	# Force the piece to the given basis.
-	var current_basis = state.transform.basis.orthonormalized()
-	var target_basis = hover_basis.orthonormalized()
-	var rotation_basis = target_basis * current_basis.inverse()
-	var rotation_euler = rotation_basis.get_euler()
-	state.angular_velocity = ANGULAR_FORCE_SCALAR * rotation_euler
+	var current_basis = state.transform.basis
+	var new_basis = hover_basis
+	if not current_basis.is_equal_approx(hover_basis):
+		new_basis = current_basis.slerp(hover_basis, ROTATION_SLERP_ALPHA)
+	state.transform.basis = new_basis.orthonormalized()
+	state.angular_velocity = Vector3.ZERO
 
 func _integrate_forces(state):
 	# Overwrite the physics forces if the piece is hovering, so we can control