I am playing Trine on PC (Steam version). Some achievements ask to collect all the Experience Potions in each level.
Some of them seems really difficult/impossible to get to me. I am wondering if I have to finish the game first in order to unblock other character abilities before I can be able to collect all potions?
Ideally, you will not need to backtrack. Because of Trine's linear progression, you won't encounter any experience orbs that you simply cannot get when you encounter them.
On the other hand, there's no reason not to finish the game before coming back and picking up the stragglers -- the later abilities (such as the wizard's floating platform) may not be required, but they can be extremely helpful all the same.
To provide evidence from experience:
I collected almost all experience in my first run of the game and then went back to collect the rest. I checked that none of the experience I missed required any skills I only gained later in the game.
Some experience requires advanced grappling-hook skills though. This includes the following case, which I consider the most difficult to obtain on a first run:
Roughly in the middle of the Crystal Caverns, you are about to cross a bridge which is almost immediately destroyed by a skeleton. The level continues through the water beneath, but the bridge led to a chest and two units of experience. Unless I missed something, this experience can only be obtained as follows:
- Rush onto the bridge immediately before it is destroyed. Since the bridge remains destroyed if you return to the last check point, the only way to retry this is to restart the entire level.
- Jump out of the water below with the thief and immediately target the the bridge’s right base with the grappling hook. Since you have to hit a small target in a short time frame, this is quite difficult.
- You upgraded the wizard’s plank skill for two planks, which you can just do with the experience just before that if you go for full experience or if you never upgraded the box skill. You then build your own bridge using one plank counterweighted with a box (or other heavy item you took with you) to shorten the gap for the second plank.
- Use skills obtained later in the game such as the floating platform.
