Really enjoyed it. I was pretty surprised after crashing my first time and seeing a completely different format of the level for the next run which was quite interesting.
I tried all ship colors(4) and found out a couple nice things.
The controls are fairly simple and the explanations at the lower part of the page aswell but you missed to add on how to start, which is holding the space bar or any click from the mouse for the count down. If using the keyboard keys, the ships will go in a straight line when pressing neither up/down except for the yellow one which is unable to move in a straight line. If using the mouse, the difficulty increases as the ship will try to stay in the same position as the arrow and will end up waving up and down along the way. It is useful to rely on the mouse since the path ahead can have tight corners, and some ships can handle better a sharp action with the mouse than with the arrow keys when moving; it also increases the difficulty a little more. For a more stable ride, use the keys.
Blue - Seems to be the most stable one. It has a nice pace and it moves pretty well both with keys and mouse. I was able to make a score of 20k easy with it. I never noticed it accelerating so I consider it to always go at the same speed.
Red - It starts off the slowest but catches up in acceleration. I was facinated by its movility with the arrow keys. It seems to be the second quickest one to react and it moves nicely with the mouse aswell. The slow start and easy mobility make it perfect to practice, though I noticed it began to accelerate as the ride progresss. I couldn't keep up with its acceleration after reaching around 15k in score. Everything seemed to move as quick as with the Green ship, if not close. Challenging none the less and probably my favourite ship of all 4.
Green - The fastest one by means since starting out. Its quick to move and react and the speed makes up for a chellenging ride. Recommended to move both with keys/mouse for its acceleration will innevitably bring you into a quick and changing ride. Blink for too long and it might end up too fast. I liked it, though I wasn't able to make up more than 13k on the score. Will surely come back to it and try to catch up to the Blue ship score.
Yellow - Starts out at a nice pace like Blue. It reacts well to keys and mouse, but it is impossible to go in a straight line unlike the rest. Its by far the hardest ship to move around, it didn't take away from the challenge of the game, if anything it increases it drastically and I was able to go out with it for a score of 9k after some rides. If using the keys, after shifting up or down, giving a suddle quick click in the opposite direction brings the ship to a quick stable point of movement, but since it can't go in a straight line it will keep inclining up or down very slowly. Recommended to try with keys but if you want to up the difficulty even more use the mouse.
When pressing the help icon at the top left I was prompt to four small squares on the right and a large rectangle on the left. When pressing the sqaures nothing showed up, so please look into it.
Overall, I really liked it. Bookmarked it as I plan to come back to it to beat my own scores again too.
Each ship keeps a different score alike. Not sure if that was intended but it was useful.
The graphics, though simple, are well presented as mentioned before by vikuserro.
The music was perfect for this sort of game and it matched with everything else.
It is a very nice game, simple, straight to the point, challenging and with a lot of potential for future updates. I'll be looking forwards to it if you plan to make improvements or add anything new.
Keep up the good work!