LemonArcade
Geometry Dash is the rhythm platformer that Swedish developer Robert Topala released through his one-man studio RobTop Games on 13 August 2013 for iOS and Android, with a PC version on Steam following in 2014. The premise has not changed in over a decade: a cube slides forward at a fixed speed, you press one button to jump, and the spikes, saws and gaps are laid out so that jumping on the beat of the music is the only way through. The version on LemonArcade is an unofficial browser recreation from FreezeNova's unblocked network, not RobTop's game, and it covers the opening levels rather than the full set of 26 official stages.
One input is all the game gives you, and it is enough. In cube form a press is a jump; touch a yellow ring mid-air and you can jump again; hit a portal and the cube becomes a ship that rises while the button is held, or a ball that flips gravity on each press. The official game added more forms over the years, including the UFO, the wave and the spider, but the early levels recreated here stay mostly in cube and ship mode, which is where the rhythm-reading skill is learned. Every obstacle is placed to the soundtrack, so once you hear the pattern you can jump to it.
Failure is total and instant: any contact with a hazard restarts the level from the beginning. The official game tracks your progress as a percentage, and every attempt that gets further than the last one is the reward. Stereo Madness, Back on Track and Polargeist, the first three levels in the original, are the ones this browser build reproduces, with their tracks by ForeverBound, DJVI and Step respectively. Their difficulty ratings in the official game are Easy, Easy and Normal, which is deceptive; each still takes new players many dozens of attempts.
Geometry Dash grew from a mobile time-killer into something closer to a platform. The official game's level editor produced millions of user levels, a rating system from Easy to Extreme Demon, and a community of players who spend months on single levels. None of that is in this browser version, and the point of a recreation like this one is narrower: it lets you learn the original's opening on a machine that cannot install the real thing, such as a school Chromebook, which is why it exists on unblocked-games lists in the first place.
It suits anyone who wants to test whether the game clicks before buying the official version, and returning players who want to re-run the first levels for fun. If you already own Geometry Dash, this offers nothing new; if you have only seen it in videos, it is the cheapest way to find out why people spend three hundred attempts on Stereo Madness.
On LemonArcade it runs free in the browser with no download or account. It works on desktop with Space, W, the up arrow or a mouse click, and on phones and tablets with a tap anywhere on the screen, which makes it one of the few games in this category that plays equally well on touch. A run through a level takes about ninety seconds, so sessions are as short as you want. Because timing is everything, a browser with audio delay or an unstable frame rate makes the game much harder than it should be.