I'm glad you liked it!
A big part of it was I've been spending time since my last jam in 2024 writing quick test projects in Godot to learn navigation, 3D imports, etc so I knew mostly how to make simple 3D games. I am working on a post-mortem though that I'll publish sometime after the results going over some of how I budgeted my time, how the game's code is structured, and some of the effects.
It also just looks a lot more complicated than it is though. Like, both the player and enemies are just PathFollow3D nodes with hitboxes attached and set to follow paths at a fixed speed. A lot of the code is also shared between objects; for example, the player, enemies, and pickups all have the same reusable health component, hitbox component, and death component objects attached to them so I only needed to write that code once at the start (Firebelley Games on YT has a great video on using composition like that). Getting the player camera to track the ship right was the hardest part and where I spent a ton of my time.
The transition effect is also fairly straightforward. I started by texturing a Panel node with one of the SciFI UI boxes, tinted it darker using the modulate property, and added a TextureRect with the stripe pattern over it (also tinted) with the add blend mode enabled in its material. That gave me a reusable door scene that I duplicated and used an AnimationPlayer to create open and close animations for them. I have a game state manager node at the top of my scene tree with all the menus, HUD, and level under it that controls when each thing is shown. Inside that node, on top of everything, is the transition scene so it covers everything when it closes (also tilted 45 degrees to look cooler). The state manager script just plays the transition scene's' open or closed animation whenever it needs to hide loading the level. All-in, the transition took about 40m to get right.