Game Design, Programming and running a one-man games business…

Category: game design

Gratuitous Tank Battles campaign map

Posted on November 4, 2011

Here is what the main ‘play battle’ screen looks like for GTB. The current plan is for three basic modes of play. The campaign scenarios, custom maps, and online maps, as shown by the three tabs at the top left of the screen.

The big map image changes to be a list of maps in the other two modes. The right hand pane shows information about the current selected map. Custom maps are ones you edited or designed yourself and saved locally. The online ones are maps you, or other players uploaded to be played by everyone else.

I still need to add in display of some high score data on that gap on the right. Also, a few of those buttons are debug-only, but you will have the option to play any map as attacker or defender, and to edit it and save it however you like.

I love company of heroes, but the map editor for it is ferociously complex, and there is no easy way to trivially change a map, then give it to a friend to play. My aim is for that sort of thing to be trivial in GTB. So when a player thinks that tile 16,24 should be place-able by the defender in map #4, he/she can just click edit, change that tile, then save it as a custom map for himself, or upload it as an ‘improved’ map #4.

That’s the theory.

Range Modifiers

Posted on October 27, 2011

This is something I really like, and comes in reply to feedback about how people hate having to guess what the underlying numbers are in tower defense games. I got it implemented today *still needs optimising…*. It’s a way to show easily the effects of a range boost augmentation for a unit. The units in GTB are built from GSB-style modules but some are ‘augmentations’ that apply to any module, such as ‘boost range by 10%’. I thought it might be cool, if such an aug is fitted, to show it as a distinct band on the range indicator when you select a unit. It’s the slightly separated strip around the edge of the range indicator for the selected riflemen.

The brighter triangle represents the firing field-of-view for that soldier. Some units have 360, like mechs, but infantry can’t swivel their hips like that :D

Thoughts?

Programming AI in a tower defense game

Posted on October 12, 2011

This is not an easy task. It is for most Tower Defense games, because they are simply scripted. The level has a set number of enemies of certain types and times, and they appear as attackers. And of course, most TD games don’t let you play as the attacker, so programming the defense AI is not needed. I need both of these to be non-scripted for Gratuitous Tank Battles.

I need attacking AI that ideally adapts mid battle to your decisions, and this is harder than it sounds. The first approach I took was to have a system with 3 types of placement timing mode (steady placement, or hoard points for a big attack or spam the current unit) and two types of unit selection (random, and select the one that has been most effective so far…with some variation).

The AI would switch randomly between these combinations and it looked pretty convincing. Sudden waves of identical units followed up by who-knows what. The problem was, it obviously did so with little care as to what it was up against.The ‘most effective unit’ code was good, because it meant totally useless designs which charged into a hail of bullets would not see much repeat business, but something major was lacking. That was the anticipating of future events.

If the defender has placed 6 machine-gun turrets (rubbish, but devastating to infantry) you shouldn’t place down infantry, regardless how well they did earlier in the battle. If they have lots of laser turrets, place down shielded units to get past them…etc.

So today, at the end of a long day of video rendering and editing, and tweaking, and bug fixing, I’m starting work on a more generic system for opponent army composition analysis, that can take snapshots of the enemy forces and realise that its 63.2% anti-shield units, and thus we should de-prioritise shielded unit selection etc.

This is annoying, fiddly, long winded code that nobody will ever see, as such, but will make Gratuitous Tank Battles a convincing challenge, which is well worth spending time on.

Working on tweaking the mechanics

Posted on October 8, 2011

It’s easy to get caught up with features, graphics, optimising and going through a checklist of items to do when you work on a game, and not set aside time to keep fiddling with the mechanics. There are an absolute ton of variations to the mechanics of any game. The only real way you know if the mechanics are right, is by trial and error.

If you wonder what the hell I’m on about with ‘game mechanics’, it’s basically the rules and systems by which the game is played. For example, in chess, the pieces all move in different ways. Some can only move forwards, some can only move 1 square at a time… None of the chess mechanics are obvious. Imagine designing it from scratch. We take for granted the idea of a knight moving over other units, or castleing, or units like bishops having infinite ‘range’, but none of them is ‘obvious’.

Right now, my bugbear is support units. GTB has repair trucks and ambulances for attackers, hospitals and repair yards for defenders. My current mechanic is this:

The support units pulse out ‘waves’ of effect at a certain interval and radius. Any damaged vehicle (repair) or soldier (hospital) within that radius at the time gets X of their health replaced.


Look! Neither side is bothering with hospitals or repair units…

This seems ineffective, and there is little real incentive to use these units. I might have just set the costs for them too high or the effect too small, but in fact i think it’s more fundamental. By the time people are losing health, they are a lost cause, and the interval between lost health and death is too slow to enable a health pulse to really do much good.

Possible solutions:

  • Ultra-rapid health pulses to ensure timing not an issue,
  • Reduce armor and shields and increase health of all units
  • Make support units dirt cheap so they are worth it anyway
  • Allow recently destroyed / killed units to be revived by the pulses.
  • Change the mechanic entirely so that the units don’t use pulses, but act as damage modifiers to protect everyone within their radius, effectively making them mobile buffs.

I’m planning on trying out the last option. It involves a lot of fiddly code, but what doesn’t eh?

BTW, stuff like this takes AGES, and it’s why I REALLY hate clones of games, where some talentless drone comes along and just copies an existing game design but slaps on some new textures. Yes, it really is easy to copy the mechanics of a popcap game, but coming up with those mechanics took a ton of work. This stuff is never obvious, and I personally don’t think it can be reliably learned from books. I think you have to just keep trying stuff.

Debug Tools and defensive AI.

Posted on October 4, 2011

Life is so much simpler when you bunch up all your hotkeys and toggles for debugging the game into a single menu. I feel like I have a rough idea what’s going on now. I also feel more confident about coding decent defensive AI when you play as the attacker:

The code for defending basically needs to manage three things. The play style (Is it spamming units, hoarding points, or steadily placing), The choice of units (Does the enemy have units weak Vs lasers? Are there lots of infantry needing flamethrowerising?) And the choice of unit placement. I’ve been concentrating on the unit placement debug UI today, so I can see what the AI is thinking when it chooses to place a turret at X rather than Y. More work to do, but currently it evaluates proximity to enemies, their size, victory-point value, closeness to the exit and proximity to the placement, plus it also has bonuses for being able to cover multiple paths from a single location.

It all needs lots of tweaking and balancing obviously, but it’s getting there. Attacking AI is much simpler.

After getting this stuff done, I’m thinking of experimenting with a unit ‘cooldown timer’ beyond a certain level to prevent spamming the same unit everywhere. Essentially there are supply delays if you plonk down 4 heavy tanks all very quickly, as new ones need to be dispatched from your offscreen HQ. I think it might be a good mechanic that encourages variety.