One approach is not to worry:
- Make several levels of medium difficulty.
- Have others playtest your levels.
- What levels did they find much harder than you anticipated? Those are hard levels.
My take on Proxima's idea:
- Place some terrain and give plenty of skills.
- Solve your level several times. Optimize the solution for skills.
- Trim the skillset to match your optimal solution.
Or:
- Play lots of levels by others.
- Build a level that combines two ideas from existing levels.
geoo's favorite:
- Play lots of levels by others.
- Submit your replays to the author.
- The author will judge some of your solutions backroutes. Sometimes, he'll also fix his levels to prevent your backroutes.
- Which backroute did you like the most? Were you surprised that he judged a particularly cool solution a backroute?
- Build a new level that has your cool backroute as the intended solution.
- I recommend to make the new level look sufficiently different from the original level. After all, the idea is now different, and it's nice to give different ideas different looks.
Draw levels on paper, mainly to brainstorm, but you can also plan details.
It's not necessary to start with an idea. You can make your level look like art first, then draw inspiration from that.
Not only the level can look like art, even the
solution can look like art. E.g., when you solve a level by Pieuw, ask yourself: Where can we place the basher/miner so that it continues the longest? Now, if your level has only one miner, has no other destructive skills, and has lots of obstactles to mine away, it'll be easy to spot the miner placement. Can you disguise* the beauty? Will the player have an a-ha effect when he finally finds the idea?
*) By disguise, I don't mean invisible things, e.g., don't hide exits/traps fully inside terrain. Everything should be clearly visible and its behavior should be obvious. Still, you can make the player wonder
which parts are important and which are merely decoration. As Icho describes: Hiding things in plain sight.
You can make levels harder by adding extra problems to a medium-difficulty level, but you'll have to test for backroutes from the extra skills.
-- Simon