Leveling up

When your experience bar reach 100%, you will level up. This will grant you 3 stat points (this is 2.5 per level if you're playing on Nightmare difficulty, which results in 2 points in a level and 3 points in the next level), 1 class talent point and 1 generic talent point, except every 5 levels where you will get 2 class talent points and no generic talent point instead. Every 10 levels you will gain a category point until level 30.

You can spend these points to upgrade your character. To do this, left click on the talent or stat you want to increase and right click to decrease.

Remember that your stat point choice is permanent. On the other hand, your last 5 class talent points and last 4 generic talent points can be reassigned later, which can be useful to test out talents.  The talents that you can reassign will be marked in cyan in the level up screen.  This can be done at any time.