Ice Age GBA 100% was the next TAS I wanted to make. I wondered what was the best possible time for TAS, it seems that the limit is 21 minutes.
In the 100% category, we have to go through the 10 basic levels as fast as possible while collecting at least 40 acorns. 40 acorns in all 10 levels unlock a bonus level. The category is completed after exiting the bonus level. There are 3 auto-scrolling levels, and 7 levels made of 10 screens each. The bonus level is different, it is composed of only 5 screens and can be finished without any requirement on the number of acorns. No warps could be used to skip an entire level, and no screen skips were discovered to this day. The challenge I wanted to take up was routing optimally the 40-acorn requirement in Manny's levels. I achieved sub 21:30, I'm satisfied with the result.
Note about the Rerecord count: Only 3524 because I optimized each segment on separated files except for the last level. Then I copy-pasted the inputs in a final file. A more accurate rerecord count would be around 20000.
The RTA time would start at frame 1148 and end at frame 77705, or a time of 21:21.79.
Many mechanics and tricks can be exploited to save frames:
- Jumps are always the same, whether we press A for 1 or many frames.
- Horizontal jumps save 1 to 6 frames over walking depending on the upcoming obstacles. So jumping as often as possible saves a lot of frames. Even on a slippery ground, jumping is faster. The main difference between a normal and a slippery ground is that on a normal ground, it is slower to jump immediately on the first frame after Manny has landed. Jumping on the 2nd frame is faster by less than a pixel. That pixel is enough to save 1 frame at the end of a screen.
- Static jumps is a trick only used in the 100% category. By pressing A and either l or r on the same frame, both Manny and the baby jump together. It allows the baby to grab acorns while Manny is in the air instead of being on the ground. Thus, Manny accelerates faster especially on non-slippery floors.
- Using Manny's trunk moves his hitbox forward and downward. Thus:
- Using the trunk before a screen transition saves 1 to 4 frames.
- Manny can jump and reach an edge sooner instead of falling.
- Manny can avoid getting hit by some high obstacles after a jump.
- Manny can grab the nuts sooner.
- Using the trunk makes Manny invincible against some obstacles like some spikes on the ground, and the groups of 3 bats. Since those obstacles are indestructible, Manny can get through those without any damage as long as the trunk animation isn't over.
- Using the trunk makes Manny land on some obstacles for a few frames instead of taking damage. Within that few-frame window, Manny can jump on a single frame or start a falling animation resulting in taking damage.
- Using the trunk against a ceiling allows Manny to stick under it. That trick is mainly used in Level 2 screen 8 and Level 5 screen 3.
- After getting hit, Manny is invincible for a short time and can get though obstacles on the ground like spikes and fires. That's useful for damage boosting.
- The obstacles are interacting only when they appear on screen. Otherwise, they are fixed. Thus, we can manipulate them with ease, especially the geysers in Level 5 screen 5.
- Bouncing on animals is slower than killing them while walking or jumping. So it is preferable to wait a few frames and kill them with the trunk rather than bouncing on them.
- Sliding on a slope is faster than jumping over it if the slope is long enough.
- A stunk affects Manny only if he touches the ground first. However, there is always a frame perfect jump possible to avoid each stunk.
- The 3 or 4-block walls can be destroyed using the trunk only twice. It is faster by 3 frames.
- In the climbing segments, we want Manny to jump as early as possible. Getting hit interrupts the jump and allows Manny to land quicker on low stairs.
- It is faster to jump instead of walking before falling from 180-degree-turn cliffs, because Manny builds much higher vertical speed.
- It is faster to release the nuts while walking instead of in the air.
- In Level 5 screen 6, it is possible to clip under the 3 groups of bats and reach the end of the screen. It is possible only because the space between those bats and the ground is wide enough. That trick doesn't work on other groups of bats, especially from level 7 and 8.
- In Level 7, it is possible to keep the ability to jump in the air after falling from icy edges. That trick is used in screens 5, 8 and 9.
- In Level 8 screen 10, it is possible to skip the snail by stomping on it because Manny's hitbox become very thin during a short time, too short unfortunately to pass under the groups of bats.
- Some rhinos can be passed without throwing a nut at them. Unfortunately, it is always slower that way. All useful rhinos can't be passed without a nut.
- A nut will respawn always 180 frames after grabbing the previous one, and can be grabbed immediately when it respawns.
- A silver nut is specific to the bonus level. Once Manny grabs one, he won't be able to use his trunk until he exits the screen or dies. Since throwing each silver nut is slow, the fewest as possible are thrown and at tactical moments.
About the RNG:
There are very few RNG in this game. The only RNG I experienced have an impact on the cycle of 1 hedgehog in level 4, falling obstacles in level 5 screen 1 and level 8 screen 2. Only the cycle of L8S2 was annoying. I had to deoptimized some screens by a frame or two in order to manipulate a faster cycle.
I hope you'll enjoy this TAS. Regards,
NinjaCocktail
