Why does my 2D character stop on slopes?

Velocity is applied horizontally; when stepping into a slope, the body collides and stops. Project the input velocity along the slope normal so motion follows the surface.

How do I detect slope normal?

Cast a Raycast2D downward from the body. ContactPoint normal gives the surface direction. Use Vector2.Perpendicular(normal) to get the along-slope vector.

Coming down slopes flies off?

Apply a small downward force when grounded to keep contact. Or use a kinematic controller that moves along the projected vector and snaps downward each step.

Fix: Unity 2D Character Sticks On Slope

Quick answer: Cast down for slope normal. Project input vector along the perpendicular. Apply small snap-down when grounded.

Player walks horizontally on flat ground. Hits a 30° slope. Stops dead. Velocity points into the slope, collision blocks.

The Fix

void FixedUpdate() {
    RaycastHit2D hit = Physics2D.Raycast(transform.position, Vector2.down,
                                          1.1f, groundLayer);
    bool grounded = hit.collider != null;
    Vector2 input = new(inputAxis * speed, 0);

    if (grounded) {
        Vector2 slopeDir = Vector2.Perpendicular(hit.normal);
        if (slopeDir.x < 0 != input.x < 0) slopeDir = -slopeDir;
        rb.velocity = slopeDir * Mathf.Abs(input.x);
        rb.velocity += Vector2.down * 5f;   // snap-down
    } else {
        rb.velocity = new(input.x, rb.velocity.y);
    }
}

Slope projection means input maps onto surface direction. Snap-down keeps contact through fast descents.

Verifying

Walk up 30° slope: smooth ascent. Walk down: stays planted. Without projection: stops at slope; without snap: bounces.

“Project. Snap. Slope walks.”

Related Issues

For BuoyancyEffector2D, see buoyancy. For trigger stay sleep, see stay sleep.

Project along slope. Stay grounded.