Your first scene: a flat 3D floor

your project so far

Assets/

Scenes/

Arena.unity

FloorMain CameraDirectional Light

Materials/

M_Floor

you already havethis lesson adds

Time to build. The target for this lesson: an empty 3D scene with one flat floor, lit, with a camera looking at it.

animated diagram

A Plane is a flat surface at Y = 0. Everything else in the game stands on top of it.

Create the project

1
Unity Hub → New project → template Universal 3D (called 3D (URP) in older versions). URP looks better and is what mobile wants.
2
Name it UnityClass. Avoid spaces, accents and Vietnamese characters in the path.
3
Once open, save the scene: File▸Save As → Assets/Scenes/Arena.unity

Add the floor

1
GameObject▸3D Object▸Plane — a 10×10 metre floor appears.
2
Rename it Floor in the Hierarchy (slow double-click, or F2).
3
In the Inspector, set Position to 0, 0, 0. Right-click the Transform header → Reset does it in one click.
4
Set Scale to 3, 1, 3 → now the floor is 30×30 metres. Plane scale 1 already equals 10 metres.

Give it a material

A Material is the colour and surface of an object. A mesh gives an object its shape; a material gives it its look.

1
In Project: Assets▸Create▸Material, name it M_Floor.
2
Set Base Map colour to a dark grey (#2B3040) and Smoothness to about 0.2.
3
Drag M_Floor from the Project window straight onto the floor in the Scene view.

Optional: a grid texture so movement is readable

Without a pattern, a flat colour floor makes it impossible to tell whether the character is moving.
Set the material's Tiling to 10, 10 with any checker texture and the floor reads instantly.

Camera and light

1
Select Main Camera. Set Position 0, 12, -14 and Rotation 35, 0, 0 — a clear, angled view from above.
2
Faster way: move the Scene view where you like it, select the camera, then GameObject▸Align With View (Ctrl/Cmd+Shift+F).
3
The Directional Light is already in the scene. Rotate it to about 50, -30, 0 for pleasant shadows.

Optional: build the floor from code instead

FloorBuilder.cs — attach to an empty GameObject

using UnityEngine;

public class FloorBuilder : MonoBehaviour
{
    public Material floorMaterial;
    public float sizeInMeters = 30f;

    void Start()
    {
        GameObject floor = GameObject.CreatePrimitive(PrimitiveType.Plane);
        floor.name = "Floor";
        floor.transform.position = Vector3.zero;
        floor.transform.localScale = Vector3.one * (sizeInMeters / 10f); // plane = 10 m
        if (floorMaterial != null)
            floor.GetComponent<Renderer>().material = floorMaterial;
    }
}