Arcane Caltrops (Revised) Version 4

You cover a 5ft radius area you can see with magical caltrops. The area becomes difficult terrain for the duration. Any creature that enters the area for the first time must make a Dexterity saving throw vs your spell save DC. On a failed save, the target takes 1 piercing damage.   On a successful dex save, the target takes no damage. On their turn, the affected target can use an action to roll a perception check vs your spell save DC to avoid the damage of walking through the caltrops. If they succeed, they are able to traverse the caltrops area without damage but the area is still treated as rough terrain and their movement speed is halved. On a failed save, the target takes 1 piercing damage for each foot they move through the affected area.The caltrops remain for the 10 minute duration or until they are dismissed by the caster.

 The spell's effective radius increases when you reach higher levels: 10 ft radius at 5th level, 15 ft radius at 11th level, 20 ft radius at 17th level.