Base After Base

Base After Base is the fifth level of both Geometry Dash versions and the first level to be rated "Hard" as of Update 2.0. This level is the final version of the level Ultimate Destruction, which was never released and was later made into this level.

Description
Base After Base produces increasingly hard jumping patterns and an antigravity section. The level begins with a difficult cube sequence, with jumps that require tighter timing, combined with jump pads and jump rings. The second half of this first cube sequence has high jumps and is trickier to judge. The end of this sequence also has trick yellow jump pads right before the first ship section, which makes it more difficult.

The next sequence is a ship segment. This is more "hall-based" than those of previous levels, with a smaller passage and spikes on alternating sides. Next, the cube takes a moment to flip upwards with antigravity, although this sequence is somewhat easier to predict than the one in Dry Out. However, it features slabs which are smaller than blocks, making it harder for the cube to judge.

Returning to normal gravity with a final few jumps leads to the completion of the level.

Secret Coins

 * The first secret coin is found after the first time the background turns red. After you jump on the ring, you will slide down, and a large flat form will block you. Instead of jumping over, slide down the hole This will make you get the coin, slide down the jump pad, and return to the normal path.
 * The second secret coin is located after the background turns completely black. After jumping many platforms, there is a spike and a space which you would avoid because it would seemingly lead you to crash. Instead of avoiding it, try to jump over the spike and through the space, and there will be an antigravity portal. It will get the hovering coin, hit a thin platform, fall down, reach a blue gravity portal, and return to the normal path.
 * The third secret coin is located at the first ship sequence after the background turns purple. When the tunnel starts, after three first spikes, you must lift your ship up and wait until you reach the hidden coin path. Hold the ship up until you have collected the coin and then go down into the normal path. This is considered easier than the normal route.

Trivia

 * The achievement unlocked by completing it in practice mode may refer to the popular catchphrase “All Your Base Are Belong to Us”, from the game Zero Wing (the achievement name is "All Your Base").
 * Base After Base was rated "Harder" until Update 1.9.
 * Completing the level takes 1:26.
 * This level is considered to be one of the easiest levels to collect secret coins along with Back on Track and Hexagon Force.
 * This is one of the four levels not to introduce a new game element. The other three are Can't Let Go, Jumper, and Theory of Everything 2.

Errors

 * At around 11%, the last spike next to the big block is missing.
 * If you take the path holding the second secret coin, you might see that both of the gravity portals are not facing towards you, therefore facing the other way.
 * There is a glitch at 40%. When you jump on to the block with another block hanging above it, if timed correctly, you can actually jump off that block and land on the next block (also with another block above it), skipping the slabs. You can do a similar glitch thrice in Can't Let Go.
 * Similarly, if you do the same thing above with a similar block at 45%, you can actually land on top of the blocks with spikes below them, instead of going the normal way. You will then fall on the next slab and continue normally.