help me with inertia !!!

Hi !
For my classic vertical shoot'em up, how to add some inertia to... my ship ???
Thanks !

Graphics 800,600


Global Player_x# = GraphicsWidth() / 2
Global Player_y# = GraphicsHeight() / 2

While Not KeyDown(KEY_ESCAPE)

	If KeyDown(KEY_LEFT) Then 
		Player_x# = Player_x# - 1.0
	End If

	If KeyDown(KEY_RIGHT) Then 
		Player_x# = Player_x# + 1.0
	End If

	If KeyDown(KEY_UP) Then 
		Player_y# = Player_y# - 1.0
	End If
	
	If KeyDown(KEY_DOWN) Then 
		Player_y# = Player_y# + 1.0
	End If
	
	Cls
                ' my ship ;-)
	DrawOval Player_x#, Player_y#, 10,10
	Flip
	
Wend

A very basic implementation could be:

Type TPlayer

	Field X:Float
	Field Y:Float
	
	Field X_Speed:Float
	Field Y_Speed:Float
	
	Const Friction:Float = 0.90
	
	
	Method Draw()
	
		DrawOval X, Y, 10,10

	EndMethod
	
	Method Update()
	
		X_Speed:*Friction
		Y_Speed:*Friction
	
		X:+X_Speed
		Y:+Y_Speed
		
		Self.Draw()
	
	EndMethod
	

EndType


Graphics 800,600

Const Offset:Float = 1.0

Local Player:TPlayer = New TPlayer

Player.X = GraphicsWidth() / 2
Player.Y = GraphicsHeight() / 2

While Not KeyDown(KEY_ESCAPE)

	If KeyDown(KEY_LEFT) Then 
		Player.X_Speed:-Offset
	End If

	If KeyDown(KEY_RIGHT) Then 
		Player.X_Speed:+Offset
	End If

	If KeyDown(KEY_UP) Then 
		Player.Y_Speed:-Offset
	End If
	
	If KeyDown(KEY_DOWN) Then 
		Player.Y_Speed:+Offset

	End If
	
	Cls
    ' my ship ;-)
	Player.Update()
	Flip
	
Wend

Many thanks for your code. How to combine this with acceleration when the ship start to move ?

If I understand you correct you can simply "adjust" the acceleration by not using the Constant "Offset", but use different Values (small Values for a slow accel, high Values for a speedy ship)