The game has 4 easy achievements. Getting them requires a few minutes of play. You don't have to complete the game to unlock all achievements.
How to Obtain All Achievements
On the start screen, walk near the red ":3", jump up. You should "stick" to the letter "C" in the text and your character will move upwards. During this, correct the "jumping" (reverse controls!) to finally get to the red ":3" place. Then press "R" to be able to start the actual game and unlock the remaining achievements.
Hint: this vertical wall traverse can be used to shorten your road in later stages.
Achievement: "The longer way"
On the start screen go to the black door with the green word "start". Then go through 3 very simple steps. Their "difficulty" is only to jump over the hole and over the hills. In the fourth stage, from the left side, the terrain consists of two inverted letters "T". The left one is "attached" to the ground and the right one hangs in the air. You should jump on the right one, not go under it.
Achievement: "Woah there, pardner!"
Go the next 2 easy steps. The next one will be a strange creature. To be honest, I'm not sure exactly what to do. I think You should get in the place of his stomach and it's worth jumping there or walking sideways. Although this achievement was unlocked for me in the next stage where the same creature was. It is also worth trying at this stage. If we want to go further, we should jump on the "speech bubble" of the creature and then on its head.
Achievement: "Cold blooded murderer"
A few stages later, we find a weapon and an enemy with his back to us. Just pick it up and shoot him.