In order to be accepted into college as a Game Design major, I had to create a board game as a portfolio piece. The prompt for the board game was that it must be themed around connection and could only use two gameplay elements besides the board and player pieces.
My immediate thought was physical connection, and for a time, the game was going to be cooperative, with the two players trying to reach each other. The gameplay elements I chose were tiles, which were used as bridge pieces to place on the board and move across; and dice, which players rolled to determine how many tiles they could place down or how many spaces they could move. However, I kept running into the same problem with this coop idea: if the goal was simply to get the two players to reach one another, then there was no challenge. They just had to keep placing down bridge tiles in the direction of one another until they reached one another.
Realizing I was hitting a brick wall, I decided to twist the idea of bridge building in a different direction. It became competitive, with the goal now being to reach the other player with your bridge to kill them before they kill you. The connection of the game now became less straightforward. One needs to approach their opponent, but puts themself at risk as well. The bridges themselves became non-Euclidian weapons, with spiky bridge ends being able to kill the opposing player like popping a balloon on a knife. The three types of bridge tiles (straight, turn, and crossroad, based on the old computer puzzle game Pipe Mania) expanded to include offensive tiles that had to connect to bridges, as well as defensive tiles that could shield from offensive tiles and didn't have to connect to a bridge. With this, the game concept was essentially set.
With the game printed and the instructions written, I had family and friends playtest the game to make sure the game was as solid as it could be, as well as making sure it was actually fun and thrilling. I found that my testers didn't fully understand the game until they were already playing it, however they learned through play quickly. That may have been bias in the testers, but it could also speak to the simplicity of control. You can only either move your pawn or place bridges, and you have to get used to building out your bridges and thus seeing all the different tiles you have at your disposal before you can reach and enter combat with your opponent.
I also found that once my playtesters were comfortable with the mechanics and rules, they quickly began strategizing ahead and pulling off multi-turn plans that I didn't even expect them to. When they were unsure about a rule however, the game came to a screeching halt, and one time I almost considered altering a rule midgame out of fear that the two players had softlocked each other and literally couldn't play any further (I didn't define how a stalemate would be resolved in the rules). With this, I understood that not only is it better to make all rules clear to prevent the game from falling apart, it's also better to make the game's framework strict and rigid. While it may seem limiting to the player, if one knows what they can't do in a game, they will focus on looking for what they can do, leading to more creative thinking. Much like how I had to design within the limits, players play more thoughtfully when they can see the limits you impose on them.
Read the game's rule book, as well as my musings on how the game turned out at the time.
Photos I took during playtesting, two of which are used above.