Aqualique 10

Aqualique 10 is a strategy game in real-time, written in 10 lines in BASIC for Commodore 64/128 computers. Written for the Basic 10-Liner Contest 2025 in the PUR-80 category.

Story

Year 2010. The days when Earth was called the Green Planet are long gone. Global human activity has led to the destruction of natural resources. Acid rain, soil erosion, poor air quality, and undrinkable water, among other effects. However, thanks to groundbreaking discoveries of new planets, water has been found on one of them. It was named Aqualique, the Planet of Water. And so, water become the new gold, mined from beneath the surface and transported back to Earth. To extract water, a group of inventors built a special water drilling extractors, called Apex. The future was looking bright...

Aim of the game

Your task is to setup a base of 250 Apex extractors in one of the sectors of the planet Aqualique.

Challenges

Unfortunately, the planet is infected with an unknown virus (called Decem-X) that spreads across the surface, destroying everything in its path. Virus colonies appear over time, so you can never be sure if another colony won't appear right next to your existing facilities. Only when the virus reaches a critical mass will it not form new colonies. However, existing colonies will spread. If that wasn't enough, the planet is notoriously hit by meteor showers. Special walls will protect you from the virus, but these walls are exposed to meteor showers. Each destroyed wall is a potential path for the virus to break into your base.

How to play

• You can build Apex water drilling extractors. One Apex costs $100,000 and by extracting water, it gives an income of $1,000 per second.
• To protect your colony from the virus, you can build a special wall for $50,000.
• Buildings appear on the surface immediately, but you have to wait to obtain funds for future investments.
• You cannot destroy your facilities or replace one with another.
• You cannot build on fields affected by the virus.
• However, area destroyed by a meteor shower is suitable for development!

Controls

• Cursor keys - move the cursor on the screen in order to place the following buildings on the surface:
• A - build Apex (the water drill extractor), cost: $100,000
• W - build a wall that protects, cost: $50,000

What's on the screen?

Left part of the top bar: price of each facility. Right part of the top bar: "$ 2000 / 0" means that you have currently $2,000,000 credits and 0 Apex extractors on the surface. Prices are provided in thousands.

• Apex water drilling extractors are displayed with a "4".
• Walls are displayed with a "=".
• Virus is displayed with a grid character.
• An area devastated by a meteor shower is displayed with a "*" character (asterisk).

Hints

• To better visualise the goal, 250 Apex extractors take up a quarter of the game screen
• There is a way to reclaim a field infected with a virus: when a meteor shower devastes the virus, you can place a wall there to expand your area, or simply place another Apex
• A single row of walls between the virus and your facilities is usually enough, but if a meteor shower destroys the wall, the virus can penetrate and start destroying everything in its path, it's safer to build double walls to better separate

Loading and running the game

Double click on the d64 image when using emulation. The program should be autoloaded. On the real hardware, just load with:

LOAD"\*",8 RUN 

The game was tested on a real hardware and with WinVice (2.4 and 3.8) and CCS64 3.9.2 emulators.

Constants and variables

• A - horizontal delta for new cursor position calculated in line 1 (-1, 0 or 1), re-used for horizontal position of new event in line 4, re-used for horizontal virus colony position pointer in line 5
• A$ - end game message ("NICE!" will be displayed on the top of the screen as only that fits!)
• B - vertical delta for new cursor position calculated in line 1 (-1, 0 or 1), re-used for vertical position of new event in line 4, re-used for vertical virus colony position pointer in line 6
• B$ - the remaining part of the pricing info that didn't fit in the first line, followed by hidden prices of buildings represented as PETSCII characters (consecutively for an apex and wall), followed by their visual representations
• C - number of credits (starting from 2000)
• D - stores the character under the cursor
• E - constant for 1064, used to offset the position of all objects rendered on the screen
• F - position on the screen where event should be set
• G - number of virus colonies established (max: 20)
• H - character under position on the screen where event should be set used in lines 7 and 8, re-used in line 9 to get the price of the building (PEEK is used to get the hidden character)
• I - used in line 3 for building (0 for Apex extractor, 1 for wall), re-used in line 4 to trigger an event (0 to set new virus colony, 1 to trigger a meteor shower)
• J - screen position when hidden "table" with building prices and their visual representation is stored (see: B$)
• K - current virus colony pointer, note that each colony is offset by 2 as horizontal and vertical position of colony is used as a pointer
• L - pointer to virus colonies table with horizontal and vertical position per colony (colony table is kept under memory position 8192+)
• M - number of existing Apex extractors
• N - constant for 8192 where colonies table is set, used to store horizontal and vertical position (in sequence) of each virus colony
• P - local virus new horizontal position offset (randomised)
• Q - local virus new vertical position offset (randomised)
• T - time counter
• U - new colony established flag, if a new virus colony has been established (U=1) or spread of an existing colony (U=0)
• V - constant for 53280, used to change colour of the screen
• W - constant for 40, as it's a common value used in various places, each usage of it saves one character of space
• X - cursor horizontal position
• Y - cursor vertical position

Scopes

• game init
• main loop
• virus colony loop
• generating the event (general and establish virus colony)
• building

Code line by line

Line 0 (game init):

• Initialise global constants and variables with READ in the following order: C, D, E, W, J, N, V, A$, B$
• Clear the screen and display both parts of the pricing info (the second part is in the B$ as it didn't fit in this line)
• Set screen foreground colour to gray #3 and background colour to gray #1
• Define function R(X) used for randomisation where X is the max value

Line 1 (main loop):

• Read the keyboard (C$ variable)
• Display the last character stored in D variable under the cursor position (so when cursor moves, the character underneath is preserved)
• On cursor keys pressed, the delta for the next position of the cursor will be set into A (horizontal position) and B (vertical position)
• Count time (T variable)
• Data for C, D

Line 2 (main loop):

• Calculate new cursor position into X and Y variables with margin applied
• Store character under cursor before drawing it into D variable
• Draw cursor in new position
• Data for E

Line 3 (main loop):

• Increase number of credits (C variable) by the number of Apex water drilling extractors when time counter is 1
• Display current number of credits and Apex extractors right to the pricing info bar
• Setting I=0 for an Apex extractor ahead and checking if "A" key was pressed, if yes, go to line 9
• Otherwise, setting I=1 for a wall ahead and checking if "W" key was pressed, if yes, go to line 9
• Otherwise, continuing in line 4

Line 4 (main loop):

• Randomisation out of 10 values if placing a new event should happen, if value is different than 5, go to line 5
• Otherwise, re-use I variable to randomise one of 2 events (I=0 to establish new virus colony, I=1 to trigger a meteor shower)
• Randomisation of horizontal (A) and vertical (B) position where the event occurs
• In case a new colony of virus was randomised to be established (I=0) and number of colonies exceeds the max (G=20), go to line 5 just to iterate through existing colonies
• Note that due to lack of space, the code below is performed even if a meteor shower should be triggered, L and U variables won't be used but there was no space to go to the next line
• Set the pointer of colony table to the last one as a new colony is triggered to be established (L=G*2)
• Set the flag that this is a new colony to be established (U=1)
• Go to line 7

Line 5 (virus colony loop):

• If no virus colonies have been established yet (G=0), go to line 1
• Otherwise, increase the pointer to currently existent virus colony (K) so it can grow in any direction
• Store current horizontal position of the iterated colony in A variable
• Randomise horizontal offset where virus spreads and store it in P variable
• Set new horizontal position of the virus by restricting the screen boundaries
• Data for W

Line 6 (virus colony loop):

• Store current vertical position of the iterated colony in B variable
• Store currently iterated virus colony (K variable) in L variable, as L variable is re-used for newly established and existing colonies to update colony pointer position
• Set new colony establishment flag to zero (U=0)
• Randomise vertical offset where virus spreads and store it in Q variable
• Set new vertical position of the virus by restricting the screen boundaries
• Set the event type to a virus (I=0)
• If number of existing Apex extractors less than 250, go to line 7
• Otherwise, display "NICE!" text on the top of the screen and END the program

Line 7 (generating the event: general):

• Calculate position on the screen where the event should be set and store it in F variable
• Get the character on the screen under which the event should be set and store it in H variable
• In case the character under the new position is an Apex extractor (H=52), it will be destroyed, so let's decrease number of active Apex extractors by 1
• If a virus colony is established (I=0), to go line 8
• Otherwise, print asterisk (POKE F,42) on the screen
• Go to line 1
• Data for J, N, V, A$

Line 8 (generating the event: establish virus colony):

• If wall is set in the new position (H=61), virus cannot get through it so go to line 1
• Otherwise, print character for virus (`POKE F,102)
• Set pointers to virus colony (POKE N+L,A and POKE N+L+1,B)
• Increase number of virus colonies (G) only if it's a newly established colony (U=1)
• Reset variable U as it's not going to be reset anywhere else
• Go to line 1
• Data for B$

Line 9 (building):

• Get the price of the building (with PEEK) and store in H variable, price is hidden on the screen (printed initially in B$ string), price of Apex extractor for I=0, price of wall for I=1
• If number of credits is lower than the price of the building, go to line 1
• Otherwise, if character under the cursor is not an empty space or the area devasted by a meteor shower (D>42), then go to line 1
• Otherwise, decrease number of credits (C=C-H)
• Get the character position under cursor in D variable (again, PEEK with +2 offset used to read it from the hidden area printed initially in B$ string), automatically it will be also restored on cursor move
• Print building on the screen
• In case an Apex extractor is built (I=0), increase number of active Apex extractors (M)
• Go to line 1

Tricks and notes

1. Aqualique 10 is based on an original game concept I created on the Amiga 500 around 1999. There was another iteration of this project, created around 2001. I also created a Commodore 64 version later on. Aqualique 10 is directly inspired visually and gameplay-wise with the Commodore 64 version, while the Apex extractor was taken from the second iteration created on the Amiga in 2001.
2. Initially, the up-arrow sign was used for the Apex extractor. However, there was no place in code to prevent building on existing virus colonies, walls or another Apex extractors and at the same time to allow building on area devastated by meteor showers. I have checked all the PETSCII characters that could resemble the shape of the Apex extractor, a design I did back then on Amiga. I quickly discovered that the "4" looked quite similar, and I even imagined it looked like it was projected from an isometric perspective! This way, I was able to apply all the logic by changing only that single object. The condition has been simplified just to a single statement in line 9: D>42.
3. Speaking of the year the game takes place in. From a 90s perspective, 2010 is a long way off when we'll all be getting around in mini-helicopters and brain transplants will be possible between exams, right?
4. Basic Abbreviator (still in alpha version) heavily assisted in writing of this game.