没有什么保险方式能够预测游戏是否会成功，但确实存在若干游戏要素，能够有效帮助作品崭露头角。显然游戏要有目标，若没有目标，体验意义何在？规则应直接了当，富有逻辑。游戏同时还应该富有挑战性；若游戏无需任何技能，你很快就会厌倦。游戏应该能够唤起玩家的想象空间或潜在好奇心；若内容不够新颖或令人困惑，很快就会变得乏味。最后，街机游戏（游戏邦注：就其定义来看，涉及很多动作）应该便于玩家轻松控制和操作。

游戏目标存在两种形式。在有些游戏，玩家逐步朝目标靠近，如《小蜜蜂》中的消灭成群入侵者，《吃豆人》中的吃掉所有豆子，或在《救难直升机》中拯救所有人质。这类例子很多，从《Scram》中的阻止核导弹工厂崩塌，到《导弹指挥官》中的遭受核导弹进攻的过程中拯救城市，或在《Ripoff》中保留所有燃料桶。不要将这两种游戏目标同过于简单的机械射击移动目标，从中换得积分的操作混淆起来。

目标需要满足玩家的期望或想象。这就是为什么有些玩家更偏好某类型的游戏。善恶交锋战斗是很多太空游戏的背景内容，其中的恶是指企图破坏地球的险恶入侵者。尽可能保护地球成为玩家的目标，同时玩家还能够在杀死外星人的过程中获得大量积分。其他富有吸引力的目标还包括在探索危险洞穴的同时收集大量财富，在危险高楼崩塌或食物耗尽前逃出其中。

电脑游戏幻想内容的魅力部分来自于其所满足的情感需求。不同幻想内容吸引不同玩家。有时幻想内容只是类似于《食物大战》中的青春期情感释放，这里你通过堆满食物的桌子同扔馅饼的主厨战斗。游戏的破坏物件虚幻内容吸引众多玩家。其表现形式可以是《Clowns and Balloons》中的将小丑从跷跷板上弹出，击破气球，或者是《Breakout》中的打破墙上的砖块。在这些情况中，部分受损的墙面或成排气球形成富有视觉吸引力的目标，同时充当形象的积分记录装置。

多数游戏的目标都隐含终点位置，或在目标实现时，或在玩家遭遇失败时。很重要的一点是，确保游戏不会永无止境地延续下去。需要设定极限范围。有时这会采用时间限制形式，有时是不断减少的弹药、小球和船只。家用电脑最常见的限制因素是加速游戏。这也是常被滥用的方式。若电脑武装兵力的进攻既非玩家能力所能接受，又缺乏机制可能性，这样的游戏速度就是在唬弄玩家。

游戏要富有挑战性，应设有结果存在不确定性的目标。若玩家确定能够达到目标或无法达到目标，游戏就无法带来挑战，玩家就会丧失兴趣。要在游戏中引入随机性非常简单，或通过隐藏重要信息，或通过引入让玩家面临灾难的随机变量。但要把握好度，因为完全基于随机性的游戏会缺乏技能元素。玩家很快会发现，他们无法控制游戏结果。

游戏中的另一更重要的设计因素是符合逻辑的系列规则。规则可以非常简单，也可以很复杂，但要行得通。游戏要遵循自己的主题，因此所有规则或变体内容都要直接从此主题中衍生。只是出于你觉得此混淆元素会让游戏更有难度而引入不匹配的游戏要素完全没有意义。例如，优秀跳跃&攀爬街机游戏《大金刚》并没有要求玩家射击所有看到的物件，而只是让他们通过回避障碍实现目标。同样，《Galaxian》这款富有难度的射击游戏通过分散游戏元素，让游戏的动态外部进攻始终保持井然有序。

《Galaxian》之类的游戏属于非对称模式，不属于平衡游戏，因为玩家和电脑外星人舰队在力量上具有不平衡性。但双方优劣势存在的差异性很小，这使得建立三角关系无法让街机游戏变得更富趣味。

所谓的三角关系是：对手能够打败其他玩家，然后又被另一玩家打败。此关系常被运用到许多游戏中，通过牺牲力量薄弱的玩家将某玩家引入圈套中。《终极战区》就是很好的例子。电脑将衬托角色置于某位置，从而促使玩家处在对抗坦克的不利位置。《时空战机》将玩家引诱至不利位置的方法更巧妙，直接根据入侵敌军的方位放置额外降落伞。其他游戏则通过奖励分散玩家。《迦楼逻王》几乎在目标出现的同时抛下燃料罐，《太空战机》会在玩家忙于同外来舰队间的炮战时呈现炸弹目标。

可变难度等级通常用于改变游戏的体验水平。这些关卡通常具有能够满足自我的名称，如星级指挥官或飞行员，能够由玩家设定。很多游戏通常会在进展中变得更具难度。递增的技能水平要求既呈现额外挑战，同时又防止玩家变得自满。通常此技巧旨在加速游戏或在战斗中放入额外敌军太空船。玩家需要能够更快更好地进行体验，在此过程中提高自己的反应能力。另一选择是在难度提高的同时给予玩家更少完成目标的时间。

设计师应谨慎操作，这样游戏的难度等级才能够稳步地从新手进阶到专家水平，玩家所获积分应稳步提高，以正向变化曲线形式呈现。曲线趋势相对平缓说明游戏更难以掌握，曲线急剧上涨意味着掌握此关卡需要一定技巧。游戏若缺乏正向曲线会令玩家感到沮丧，因为其未能提供适当机会，让玩家提高自己的积分。

优质游戏都会提供进展奖励及不同难度等级。通常，游戏会给予玩家积分、额外小球、船只奖励或是向积分超越一定临界值的玩家提供更多弹药。更重要的是，获胜奖励比失败沮丧感更重要。游戏要融入玩家的自我意识。玩家想要战胜富有挑战性的游戏，他们不希望每次失败都受到侮辱。

理想街机游戏应在各体验等级中呈现可战胜的幻觉。其中的关键要素是清晰而简单的游戏设计。太多细节或太多规则会吓跑玩家。若玩家觉得其失败是由复杂游戏的瑕疵或控制装置所导致，那么他会觉得游戏缺乏公平性，然后选择退出。相反，若玩家觉得失败是由自身能够修正的错误所引起，那么他会觉得游戏能够战胜，会反复进行体验，然后掌握游戏。这就好像玩家自己要求自己再玩一次。

激发玩家的好奇心能够有效保持游戏趣味性。虽然创新性有时是原生作品的关键要素，但若游戏鲜有深度，它就会变得重复而乏味。备受众多发行商青睐的一个方法是，让游戏在发展过程中切换至各略有不同的情境。有些游戏改变对手，而有些游戏则变换情境；有些游戏则兼容二者。若玩家想要满足自己的好奇心，他需要超越他人。《Threshold》这类游戏基于24组不同外太空飞船前进；《Vanguard》的风景和外星太空飞船都发生改变，能够有效刺激玩家的好奇心。

这些能够激发玩家游戏兴致的元素就是所谓的“Perks”（特殊能力）。它们在玩家认为自己能够完全把握游戏的情况下起到的作用最显著。Perks的设定时机要把握得很好，这样玩家才不会因为游戏内容出现过缓或过快而退出游戏。最常见的特殊能力是额外生命。不妨参考这些投币式电子游戏：《吃豆人》、《大金刚》、《挖金子》、《Joust》、《Marto Bros.》和《Tempest》。这些游戏都呈现多种屏幕图像。不同屏幕内容身就是特殊能力，但这些游戏存在的共性是获得额外生命奖励的时间。玩家通常会在进入第三道屏幕画面时享受到额外生命。这几乎不太可能是巧合情况。这些画面基于特定速率设定，多少取决于玩家的技能。第三道屏幕的额外生命会在玩家被激怒前出现，所以不要拖15分钟才出现。新手玩家也通常在此阶段丧命。

有些游戏会在中间插入卡通动画活跃游戏气氛。玩家的兴致会因卡通动画而重新燃起。对许多玩家来说，目睹下个卡通动画已变成他们的个人目标。植入连规则都没有提示的隐藏功能是另一设计巧妙的特殊能力。这些装饰品留待富有经验的玩家进行探索。这些元素能够让那些已被熟练玩家厌倦的早期关卡重新发光发亮。例如，在投币式《星际大战》中，玩家会听到Obi-Wan Kenobi劝他们采用Force（原力）。游戏指示完全没有告诉它们怎么做。只有通过试验，玩家才会发现自己需在没有开枪的情况下飞过战壕，这样他就能够在到达排气口的时候获得大量额外积分。高分功能也可以被视作“特殊能力”。虽然这无法激活游戏中的趣味元素，但其重要性在于它能够呈现游戏的体验趣味，即便游戏只是款非常平凡的作品。高分本身就是供玩家实现的个人目标（游戏邦注：无论是突破自己的高分，还是超越他人的成绩）。

有时在游戏过程中变化玩家的情感反应也是种“特殊能力”。偶尔在紧张射击活动中穿插滑稽场面，紧张气氛能够有所缓解，有趣的游戏有时需要融入若干感人瞬间。记住游戏作为愉快活动需要具有对比性。总之，特殊能力数不胜数，但它们的目标都一样：在玩家厌倦前重新激活游戏趣味性。

游戏的可控制性是设计过程中的一大注意事项。有时这指人体工学。设计师通常在键盘和游戏棒/控制杆控制装置中进行选择。当眼手协调基于游戏棒或控制杆更富效率时，尝试制作包含更多控制功能的程序员将选择键盘控制机制。有时，他们制作的游戏需要9-10个按键，但遗憾的是，这只有钢琴家能够操作。控制装置需花费很多时间掌握的游戏通常很容易带来沮丧感。

能够准确控制动作非常重要。若屏幕无法即时反应玩家的输入内容，玩家就会觉得发生错位，感到非常沮丧。程序员需要谨慎对待设计，确保游戏能够正确回应玩家。例如，不应让玩家觉得电脑在迷宫游戏中拐错弯。

显然，雅达利用户喜欢能够提供有竞争性电脑对手的游戏。在若干多人游戏中，2人或更多人组合会同时进行竞争。这些比赛很多都是包含2-4人玩家的运动或纸牌游戏。合作型游戏很少见，除非是在电脑竞争者非常熟练的情况下。街机游戏《Ripoff》包含电脑对手，这不仅仅是两位玩家同时体验的比赛。战斗非常迅速和激烈，团队成员的船只需受到保护，让其免受伙伴子弹的攻击。家用电脑版《Wizard of Wor》提供竞争型或合作型体验选择。这是款颇有难度的游戏，若玩家想要进入更高关卡，那就需要进行合作型体验，但这款游戏的合作是通过协议。若你不慎犯错，伙伴甚至会得到1000积分。看到某玩家无心走入其他玩家的射线后，合作体验变成激烈竞争着实非常有趣。

截至目前，我们已谈到如何提高游戏重玩价值，吸引公众眼球。热门作品的具体例证能够让你对自己的设计有更深入的理解。

街机游戏范例

《太空入侵者》是首款非常热门的街机游戏。游戏目标是防御草坪免受残忍外来入侵者的攻击，他们会通过系列炮火攻击你的城堡和枪械基地。这是款限时游戏，在敌人成群进入地下，破坏玩家的枪械基地前，他们只有有限时间消灭此进攻浪潮。

消灭外来入侵者的所有操作都是很好的视觉积分记录装置。玩家永远无法获胜，只能是让自己尽可能存活更久。但消除进攻浪潮的各操作都是延缓玩家步入消亡的中间目标。随后的关卡会变得更难，因为发动进攻的外来入侵者每次都会朝地面更近一步，缩减玩家消灭他们的有限时间。敌人逐步朝移动枪械基地靠近，这让玩家回避敌人枪火的反应时间变得越来越短。

《Sneakers》、《Galaxian》、《Threshold》和《Galaga》之类的射击游戏其实是“太空入侵者”主题的衍生内容。无论是基于太空，还是基于地面，每款游戏都基于玩家的破坏性操作设置系列目标。目标或进攻者不再处于静态。他们或躲闪你的枪火，或发动自杀性的进攻。

这类游戏的强大吸引力在于能够激发好奇心及存在游戏深度。游戏促使玩家争取在每回游戏中表现更好，他们只是想知道进攻者在下个关卡中会是什么样子，他们所采取的策略是什么。设计目标多种多样，后续目标会比前个目标更具难度。虽然很多游戏都提供无限制的子弹，但《Threshold》则是通过过度加热玩家的激光器，从而控制快速、随机和浪费的炮火。因此，玩家在游戏中的射击需准确而有节奏。

《吃豆人》的风靡要归功于游戏的设计。首先，游戏再现玩家童年时期的梦境。作为孩子，我们都曾梦到自己被怪兽或幽灵追逐，我们觉得自己无法阻止他们。我们希望自己能够掌握某些扭转时局的渠道，只要某些时刻就行。《吃豆人》的4个能量豆就满足此幻想。关于在各关卡吃剩的豆子，游戏还提供视觉反馈。清除个人关卡属于即时目标，因此就连新手玩家都觉得自己能够清除关卡。由于《吃豆人》是款消耗型游戏而非破坏型游戏，它因此受到男女玩家的追捧。

对更高水平的玩家来说，游戏就变成学习体验，因为幽灵会遵循可识别的非随机模式。玩家最终将能够预测自己的行动，然后能够在某特定关卡中清除所有豆子。游戏的长期目标是继续存活和获得高分。游戏旨在让玩家在表现更好的同时获得更多乐趣。因此，玩家愿意投入时间和金钱学习游戏。

而在《Super Cobra》、《Vanguard》和《Tail of Beta Lyrae》这类的滚动游戏中，玩家的船只要穿梭于多屏幕空间中，其优点在于能够激发玩家的好奇心，呈现视觉多样性。《Vanguard》（游戏邦注：这是款射击游戏，游戏中许多敌方的船舶和生物会攻击你的船只）设有蜿蜒的隧道，其中穿插各类小空间。游戏融入众多截面，还有从水平切换到对角，然后再转变成垂直位模式的滚动方向，这就好像同时体验各种不同的街机游戏。游戏中玩家享有多次机会选择进入战斗中，其主要武器是有时间限制的通电宇宙飞船（主要用于攻击敌人），或者只是4个平凡而古老的双向激光器。出现于下方角落的地图主要告知玩家进展情况。这款游戏的好奇因素非常诱人，游戏腾有30秒钟时间诱惑玩家投入额外15分钟，继续之前的内容。

《Super Cobra》是款非常经典的游戏，游戏中玩家驾驶直升飞机穿过滚动的外星领域或层层设防、障碍遍布的狭窄隧道。起初，玩家需要回避地面发射的火箭及若干激光基地，但随着游戏的进展，玩家需要同流星和外来船只对抗。通过炸弹或激光器清理隧道中的突出地面目标是获得生存的关键。轰炸准确性也非常重要。若你无法通过击中能量存储目标补充自己的能量供应，游戏很快就会结束。

《Pole Position》是款具有高度竞争性的游戏，其吸引众多玩家的原因是，游戏有效将虚幻元素同现实元素结合起来。游戏满足玩家变成赛车手而又无需承受任何危险的期望。发生碰撞永远不会产生毁灭性结果，不会终止游戏。游戏的目标是争取获得比赛资格及完成比赛。从某种意义上看，这是非常逼真的模拟情境，玩家需要换挡，及在滚动道路上准确调整方向。玩家基于三维视角浏览道路和车子，仿佛自己就在后面的50英尺处，有点身临其境的感觉。

谈到虚幻游戏，《Joust》马上就会映入我们的脑中，游戏背景是骑士精神盛行的中世纪。游戏呈现的画面不是两位身着光鲜盔甲的骑士在马背上决斗，而是让玩家驾着类似于鸵鸟的装置在空中进行战斗。玩家不会直接射击对手，而通过自己的座驾和长矛攻击对方的座驾，有时很温和，有时很猛烈。处在较高位置的座驾最终总是能够获得胜利。玩家能够在毫发无损的情况下感受到真实冲突的快感。

游戏不断促使玩家采取行动。玩家需持续点击动作按键，保证座驾处于飞翔状态。当玩家在屏幕切换间隙进行短暂休息，其所操作的道具也会处于停止状态（游戏邦注：不会像在其他游戏中那样，还会继续漫无目的地飞翔）。两个玩家能够同时进行体验，但无需达成合作关系。屏幕底部的Lava Troll（熔岩巨魔）是玩家和敌人所面临的额外危险情境。Lava Troll试图抓住周围的物体，将其扔入熔岩中。这有时能够对玩家起到一定帮助，因为熔岩能够禁锢敌人，方便玩家进行攻击。关于在更高关卡中出现的更可怕敌人翼手龙，玩家需要想办法打败它。作为额外能力，游戏每隔5道屏幕就会出现额外关卡，其中玩家无需同任何人战斗，只是单纯通过捡鸡蛋获得额外积分。通常，这都能够给玩家带来额外生命，或者至少是在游戏空间中进行短暂休息。肢体接触、独创性、即时玩家参与及怪兽互动都是促使这款获得成功的关键要素。

有些设计非常巧妙的游戏可以归类成独创游戏。这些通常是通过人类或动物角色代表玩家的“可爱”游戏。这些独创游戏或遵循拯救他人的主题，或需要玩家具有很好的灵活度及准确定时技能，以避免惨败或主角死去的情况。

这些拯救主题出现在《大金刚》、《Donkey Kong Junior》、《Fantasy》和《Adventures of Roby Roto》之类的游戏。拯救情境通常鲜少发生，但此主题将玩家从游戏某内容带入下一内容。在《大金刚》和《Fantasy》中，女孩会在玩家到达前进入下个屏幕情境中。游戏目标不是进行拯救，而是克服挡道的障碍。玩家通过重复体验掌握模式及如何准确定时，从而提高自己的技能。

虽然扮演主角在这些游戏中很少见，但有两款游戏都遵循此主题：街机上的《The Adventures of Roby Roto》和微电脑上的《救难直升机》。就两款游戏来说，后者更加纯粹。成功基于获救人质衡量。玩家也许在完成任务的过程中摧毁27台敌军坦克和飞机，但这些都无法提高积分。因此，虽然人质的挥手示意能够引起其他人质的同情，但游戏的魅力仅仅存在于扮演主角所带来的自我满足感。

在最后一组独创游戏中，玩家需回避导致丧命的灾难。这些游戏的目标和阻碍变化很大。《疯狂爬梯者》要求玩家攀登上高楼，但这是在窗户紧闭阻碍通道，及愤怒的房东试图将其击落，用花盆撞击玩家头部的情况下进行。《Frogger》需要玩家勇敢面对有关准确定时技能的考验。要在丛林Hunt中扮演Tarzan需要灵活性和定时技能，只有这样玩家方能像荡秋千演员演员那样在藤条间来回穿梭或是冒险尝试瀑布。在所有这些游戏中，可爱特点是游戏首先吸引玩家眼球的地方，但定时技能及游戏深度的发展则能够促使玩家持续体验。同样，此构思非常多元化，难度水平会逐渐递增。

街机游戏存在莫名的力量让玩家觉得自己的失败只是意外，若玩家多试一次，就能够战胜游戏。若你能够设计出有趣而令人兴奋的作品，同时融入此额外特点，那么这就是款富有沉浸性的游戏，你梦寐以求的财富就会随之而来。

设计建议

我们能够提供给游戏程序员最好的建议就是，在开始编程前仔细设计游戏。首先确定想要获得的结果，然后弄清所需的操作。若这行不通，不妨调整构思或目标，直到找到满意的元素。确保游戏遵循现实世界的物理原则，这样游戏就能够符合玩家的直觉（游戏邦注：例如当物体从某高处落下时，会破裂或弹起）。

很多新手程序员都倾向于立即在屏幕上呈现游戏内容。这种技巧没有什么问题，毕竟它能够鼓励你继续进行操作。但很多设计师基于渐进原则设计自己的游戏，添加看起来不错或需要更多操作的内容。这产生的结果是他们迅速失去玩家或角色，被迫进行痛苦的重写。

每个人都希望以不同方式组织自己的游戏。有些人，例如我，更喜欢结构紧凑的流程图；其他人，比如我的伙伴，则只是粗略写下游戏系列事件的纲要。你偏好哪种形式？我们强烈建议你将自己常用的惯例设立成独立子程序。这种方式会简化主代码循环的逻辑。

我们在谈到这些作品前，都有仔细进行剖析。这意味着在我们看来，屏幕记忆、可弹出画面记忆、角色组合和真实游戏代码这类的元素都处于存储器中。我们粗略描绘游戏的主要逻辑循环，一步步编写代码，但这总是行得通，或者至少应该行得通。（本文为游戏邦/gamerboom.com编译，拒绝任何不保留版权的转载，如需转载请联系：游戏邦）

Game Design Theory

There is no sure-fire way to predict whether a game will be successful, but there are certain attributes that contribute to success. Certainly a game should have a goal without one, what is the point in playing? Rules should be straightforward and logical. The game should also be a challenge; if it requires no skill, you will quickly tire of it. A game should evoke either fantasy or your innate curiosity; if it isn’t novel or puzzling, it becomes boring. And lastly, arcade games, that by definition have a lot of action, should be easily controllable.

Game objectives take two different forms. There are games where you gradually approach the goal, like destroying a fleet of invaders in Galaxian, eating all the dots in Pac Man, or rescuing all of the hostages in Choplifter. There are other games where the goal is to avoid catastrophe. Examples of this range from preventing a nuclear power plant meltdown in Scram, to saving your cities during a nuclear missile attack in Missile Command, or preserving all of your fuel canisters in Ripoff. Do not confuse these two kinds of game objectives with the simplistic and mindless act of scoring lots of points by shooting everything that moves.

Goals must suit a player’s expectations or fantasies. This is why certain people like certain types of games better than others. The battle lines of good against evil lurk in the background of many space games, wherein evil, menacing invaders are bent on the destruction of Earth. It becomes the player’s goal to protect the Earth as long as possible while scoring the most points for killing aliens. Other appealing goals range from accumulating the most treasure while exploring a dangerous cavern, to escaping from a crumbling building before it collapses or your food runs out.

Computer game fantasies derive some of their appeal from the emotional needs they satisfy. Different fantasies appeal to different people. Sometimes the fantasy is simply an adolescent emotional release as in Food Fight, where you battle piethrowing chefs with tables full of messy food. The fantasy of destroying objects during a game appeals to others. It can take the form of popping balloons by bouncing a clown off a teeter-totter, as in Clowns and Balloons, or breaking out bricks in a wall, as in Breakout. In each case, the partially-destroyed wall or rows of balloons presents a visually compelling goal and a graphic scorekeeping device as well.

Goals in most games imply an end point, either when the goal is reached or when you fail, It is often important to make sure the game doesn’t just go on and on forever. Limits should be set. Sometimes these take the form of time limits or constantly diminishing amounts of ammunition, balls, or ships. The most widespread limiting factor, at least on home computers, is speeding up the game. it is also the most abused. A game tempo, where it is neither humanly nor mechanically possible to withstand the onslaught of the computer’s forces, cheats the player.

For a game to be considered challenging, it should have a goal where the outcome is uncertain. If the player is certain to reach the goal or certain not to reach it, the game is unlikely to present a challenge, and the player will lose interest. It is very easy to introduce randomness into the game either by hiding important information or by introducing random variables that draw the player toward disaster. Be careful not to overdo this, since a totally random game lacks a skill factor. Players quickly discover that they have no control over the outcome.

One of the more important design elements in any game is a logical set of rules. The rules can be extremely simple or utterly complex, but they must make sense. Since the game must follow its theme, any rules or variations should stem directly from that theme. It is pointless to throw in game elements that simply don’t belong just because you think that confusing the player would make the game more difficult. For instance, Donkey Kong, one of the best jumping, climbing arcade games, doesn’t require the player to shoot everything in sight, just avoid obstacles to reach the goal. Similarly, a tough, shoot-’em-up game like Galaxian keeps its fluid alien attack uncluttered by distracting game elements.

A game like Galaxian is considered asymmetric. It is not a balanced game because both the player and the computer’s alien fleet are unbalanced in strength. Yet the differences between the advantages and disadvantages of the two opponents are too similar to build triangular relationships that make an arcade game more interesting.

The triangular relationship is one in which each opponent can defeat one other or be defeated by the third. The relationship is often used in many games to lure the player into a trap by sacrificing a weakly-armed player. Battlezone is a good example. The computer maneuvers the saucer to entice the human into a poor position against the tank. Time Pilot lures you into a poor position more subtly by placing the bonus parachute directly in line with the incoming enemy fighter pack. Other games use the bonus to distract you. Sky Blazer nearly always drops a fuel canister just at the time that your target appears, and bomb targets come up in Xevious just when you are engaged in a heavy fire fight with the alien armada.

A variable difficulty level is often used to alter the game’s level of play. These levels, often with ego-satisfying names like Star Commander or Pilot, can be set by the player. Many games are designed to become harder the further you progress. The increasing skill level requirement presents an added challenge, while preventing the player from growing complacent. Often the technique is to speed up the game or place additional enemy craft into battle. The player is required to play faster and better, honing his reflexes during the process. Another variation allows less time to complete your objective as the difficulty increases.

Care must be taken so that the game’s level of difficulty progresses evenly from beginner to expert level, Players’ scores should reflect a steady improvement in what is known as a positive monotonic curve. A game with a relatively flat curve is hard to learn, while a sharp jump means that there is some trick required to master the level. Games that don’t have a positive monotonic curve frustrate players because they fail to provide reasonable opportunities to better one’s score.

Any good game should offer a reward for reaching increasingly. difficult levels of play. Often, bonus points, extra balls, ships, or more ammunition are rewarded for exceeding score thresholds. It is important that the rewards for winning outweigh the disappointment of losing. A player’s ego is involved. A person wants to beat a challenging game, not be humiliated each time he loses.

The ideal arcade game should foster the illusion of winnability at all levels of play. One important factor is a clean and simple game design. Too much detail or too many rules may intimidate the player. If a player believes that his failure was caused by a flaw in an overly complex game or by the controls, he will consider the game unfair and quit. On the other hand, if a player perceives failure to be attributed to correctable errors on his part, then he believes the game to be winnable and will play repeatedly to master the game. It’s as if the player teases himself to play one more time.

Appealing to a player’s curiosity effectively keeps a game interesting. While novelty is sometimes a crucial factor in the original purchase, if the game has little depth, it becomes repetitious and boring. One method that appeals to many game designers is to have the game progress to slightly different scenarios. Some games change the opposition, while others vary the scenery; some do both. The player has to excel if he is to satisfy his curiosity. Games like Threshold, which progresses through twenty-four sets of alien spacecraft, or Vanguard, in which both the scenery and alien craft changes, offer strong curiosity incentives.

These spurs to a player’s interest in the game are called “Perks.” They are most important just when the player thinks he has the game figured out. Perks must be carefully timed so that the player does not give up on the game because not enough happens soon enough or because everything the game has to offer has been seen too soon. The most common perk is an extra life. Consider these coin-op video games: Pac Man, Donkey Kong, Dig Dug, Joust, Marto Bros., and Tempest. These games have multiple screens. The different screens by themselves are a perk, but what these games have in common is the time at which an extra life is rewarded. The extra lives generally come to the average player at some point in his third screen. This is hardly coincidental. The screens are scheduled at a specific rate, somewhat dependent on the player’s skill. The extra life on the third screen comes in just before the average player might become exasperated and so not put in another quarter. The novice player is usually out of lives at this point, too.

Some games use cartoon intermissions to perk up the game. The player’s interest is renewed with each cartoon. For many players, seeing the next cartoon becomes a personal goal. Placing hidden features not even hinted at in the rules is another clever perk. These embellishments are left for the experienced player to discover. They can even brighten up the earlier levels of a game which has become dull for the expert. For example, in the coin-op version of Star Wars, players hear the voice of Obi-Wan Kenobi admonishing them to use the Force. Nothing in the game instructions tell them what to do. Only by experimentation will a player realize that he must fly through the trench without firing a shot to receive a substantial point bonus upon reaching the exhaust port. The high score feature can also be considered as a “perk.” While it doesn’t renew interest within the game, it is important because it can renew interest in playing even a mediocre game again. The high score itself presents a personal goal to reach, whether it be to beat your own high score or someone else’s.

Sometimes varying the player’s emotional response during the game serves as a “perk.” Tension can be relieved during a tense shoot-’em-up with occasional comic relief, while cute games sometimes need touching moments. Remember games as entertainment need contrast. In sum, the varieties of perks are endless, but their objective is the same: renew interest in the game before the player becomes tired of it.

A game’s controllability is one of the more important considerations in design. It is sometimes referred to as human engineering. Designers usually choose between keyboard and paddle/joystick control. While eye/hand coordination is more effective with paddles or joysticks, programmers attempting to create games with too many control functions will opt for a keyboard control system. At times, they produce a game that requires nine or ten keyboard controls which, unfortunately, only a pianist can operate. Games whose controls require considerable time to master often prove frustrating to play.

The ability to accurately control the action is crucial in the I design. If the screen does not respond immediately to the player’s input, the player may end up feeling out of sync and become frustrated with the game. The programmer must insure through careful design that the game responds properly to the player. The player shouldn’t believe, for example, that the computer made a wrong turn for him in a maze game.

Apparently, Atari owners like games which pit them against a competitive computer opponent. In several multi-player games, groups of two or more simultaneously compete against each other. Most of these contests are sports or card games involving two to four players. The cooperative game is rarely seen, except in cases where the computer competitor is much too skillful. The arcade game Ripoff involves a computer opponent that is more than a match for two players playing simultaneously. The battle is so fast and fierce that the teammate’s ship has to be protected from his partner’s bullets. The home computer version of Wizard of Wor offers a choice of competitive or cooperative play. It is a tough game that really needs cooperative play if the more advanced game levels are to be reached, but cooperation in this game is by agreement, not by mutual invulnerablity. Your partner is even worth 1000 points if you mistakenly blunder. It is quite interesting to watch cooperation turn into a fiercely competitive game after one player inadvertently walks into the other player’s line of fire.

So far, we have discussed theory and generalizations that should increase a game’s playability and appeal to the public. Concrete examples of the more popular games should give you a much more solid foundation for your own designs.

Example Arcade Games

Space Invaders was the first really popular arcade game. The object is to defend your turf against an alien horde of ferocious invaders who attack your castles and gun bases with a barrage of undulating bullets. It is actually a timed game, since you only have a limited period to destroy the entire attacking wave before they descend to the ground in marching formations and overrun your lone gun base.

The elimination of each alien acts as a visual scorekeeping device. You can never win, only survive as long as possible (thus getting the maximum playtime for your quarter).
Elimination of each attacking wave, however, is an intermediate goal that staves off your inevitable doom. Each successive level becomes more difficult since the aliens, which begin their attack increasingly closer to Earth each round, limit the amount of time that you have to destroy them. Their constant approach to your mobile gun base decreases the reaction time needed to avoid enemy fire.

Shoot-’em-up games like Sneakers, Galaxian, Threshold, and Galaga are actually spin-offs of the Space Invaders theme. Whether they are set in space or on the ground, each has a variety of targets bent on your destruction. The targets or attackers are no longer static. Either they appear to dodge your fire, or they resort to kamikaze-type attacks.

The strong appeal of these types of games is based on curiosity and game depth. You are inspired to do better with each game just to see what the attackers are going to look like in the next level and what their tactics might be. The design goal is variety, with each successive level slightly harder than the last. Although most offer an unlimited number of bullets, Threshold controls rapid, random, and wasteful firing by overheating your lasers. Thus, your firing must be more accurate and paced during the game.

The popularity of Pac Man can be attributed to the game’s design. First, it satisfies the fantasy concept of a person’s childhood dreams. As children, we dreamt that we were being chased by evil monsters or ghosts, and we felt powerless to stop them. We wished that there were some way to turn the tables, if only for a few moments. Pac Man’s four energy dots fulfill that fantasy. The game also offers the visual feedback of the number of remaining dots to be eaten at each level. And since clearing each individual level is an immediate goal, even beginners believe a level can be cleared. Because Pac Man is a game of consumption rather than one of destruction, it appeals to players of both sexes.

The game becomes a learning experience for the more advanced player, since the ghosts follow a discernible, non-random pattern. A player is eventually able to predict their movements and, consequently, to develop a technique to clear all of the dots on a particular level. The long term goal is survival and the highest score. The game is designed so that you gain more pleasure as you get better. Thus, players are willing to devote the time and money to master the game.

Scrolling games, such as Super Cobra, Vanguard, and Tail of Beta Lyrae, wherein your ship travels over a multi-screen world, benefit strongly from player curiosity and visual variety. Vanguard, a shoot-’em-up game in which a variety of enemy vessels and creatures attack your ship, has an extremely long sinuous tunnel with various types of chambers. The game has so many sections, combined with scrolling directions which change from horizontal to diagonal to vertical, that it is like playing many different arcade games at once. The player is given the option several times during the game to enter battle with a time-limited, energized spacecraft equipped for ramming the enemy, or merely four plain, old directional lasers. A map displayed in the lower corner informs the player of his progress. The curiosity factor is so enticing in this game that thirty seconds are provided to lure you into inserting another quarter in order to continue from where you left off.

Super Cobra is a classic game wherein you fly a helicopter over scrolling alien terrain and through heavily fortified and obstacle-filled narrow tunnels. Initially, you have to survive ground-launched rockets and a few laser bases, but as the game progresses you must also contend with meteors and alien ships. Using either your bombs or lasers to clear the tunnels of protruding ground targets is crucial to your survival. Bombing accuracy is also important. If you don’t replenish your fuel supply by hitting enough fuel depot targets, your game will soon be over.

Pole Position, a highly competitive game, appeals to many players because it mixes just the right amount of fantasy with reality. It fulfills the fantasy of being a race car driver without the inherent danger. Crashes are never fatal and do not end the game. The goal of the game is to qualify for and complete the race. In a sense, it is a very realistic simulation requiring shifting gears and precise steering on a scrolling roadway. The player has a three-dimensional view of the course and his car, as if he were following it from fifty feet behind, a sort of out-of-body effect.

Joust immediately comes to mind when discussing a pure fantasy game that traces its roots to the glamorous days of medieval chivalry. Instead of presenting two knights in shining armor dueling on horseback, Joust allows the player to fly his ostrich-like mount to do battle in midair. The player does not shoot his opponents but defeats them by ramming his mount and lance into theirs, sometimes delicately, sometimes violently. The higher mount always wins. The player gains the excitement of physical contact without a bloody nose.

The game constantly forces the player into action. He must keep hitting the action button to make his mount fly. When the player takes a short rest between screens, his surrogate also rests and does not continue to fly along aimlessly as it might in other games. Two players can play simultaneously but are not forced into partnership. The Lava Troll on the bottom of the screen is an additional menace both to the player and his enemies. It attempts to grab at anything close enough and drag it into the lava. This sometimes works to the player’s advantage, since the lava can imprison an enemy and make it easier to destroy. A more formidable enemy, the pterodactyl that appears on higher levels, requires the player to discover a way to defeat it. As an added perk, every fifth screen is a bonus level where the player need not fight anyone but simply pick up the eggs for additional points. Many times this earns the player an extra life or at least a temporary rest from the game’s pace. Physical contact, originality, immediate player involvement, and monster interaction are key parts of this game’s success.

Some of the most clever games can be classed as novelty games. These are often “cute” games involving human or animal characters with which the player can identify. These novelty games either follow the theme of rescuing someone, or require the player to develop good manual dexterity and precise timing skills in order to avoid catastrophe or the demise of the hero.

The rescue theme appears in games like Donkey Kong, Donkey Kong Junior, Fantasy, and the Adventures of Roby Roto. In many cases an actual rescue doesn’t take place, but the theme carries the player from one portion of the game to the next. In both Donkey Kong and Fantasy, the girl is whisked away to the next screen just before the player reaches her. The objective isn’t the rescue but to overcome the obstacles barring your way. Learning the patterns and precise timing through repeated play hones the player’s skill.

Although playing the hero is rare in these games, two games have followed this theme: The Adventures of Roby Roto in the arcade, and Choplifter on most microcomputers. The latter is probably the purest in theme of the two. The rescue of sixty-four hostages is the one and only goal. Success is measured in the number of hostages rescued. The fact that the player may have destroyed twenty-seven enemy tanks and planes during the mission adds nothing to the score. Thus, while details
like the hostage’s waving builds empathy for the hostages, the appeal is simply the ego-satisfying role of playing the hero.

In the final group of novelty games, the player must avoid the calamity of losing a life. The goals and obstacles in these games differ widely. Crazy Climber requires the player to scale a building while windows close to block the path, and angry tenants, attempting to knock the climber off the building, drop flower pots on his head. Frogger has the player brave traffic in a test of precise timing skills. And playing Tarzan in jungle Hunt requires dexterity and timing skills to swing from vine to vine like a trapeze artist, or risk death in the fall. In each of these games the cuteness is what first attracts the audience, but it is the development of the player’s timing skills and game depth that keeps him playing. Again, the concept is variety, along with increasing levels of difficulty.

Arcade games have that indefinable ability to make you feel that your losing is just a fluke, and that if you play just one more time, you’ll beat it. If you can design a game that is fun and exciting to play, and has that added quality, then you have designed an addictive game, and wealth beyond your wildest dreams may be yours.

What Can Go Wrong

The best piece of advice that we can give a game programmer is to carefully plan out your game before you begin programming it. First decide what results you want and work backwards to figure out what you have to do to get them. If it doesn’t work, change your concept or goal until you get something you are satisfied with. Make sure the game follows real-world physical principle, so that it feels right on a gut level. For example, objects smash or bounce when they fall from any height.

Many novice programmers try to get something up on the screen immediately. Actually, there is nothing wrong with this technique. After all, it does give you some encouragement to continue. However, most develop their games on a piecemeal basis, adding something because it looks good or because they need more action. The result is that they soon run out of players or characters and are forced to do a very painful rewrite.

Everyone prefers to organize his game differently. Some, like me, prefer the tight- structured approach of a flowchart; others, like my partner, just write down a rough outline of the order of events in the game. Whichever approach you prefer, we strongly recommend that you develop many of your frequently used routines as independent subroutines. This approach simplifies the logic of the main code loop.

We carefully planned all of the games in this book before we wrote them. This means that we considered where items like screen memory, player-missile memory, the character set, and the actual game code were placed in memory. We roughly flowcharted the game’s main logic loop. We then wrote the code in small chunks, but in such manner that it always ran, or at least was supposed to run.

The first priority was to draw the playfield. This generally means that we had to get the display list right and move the character set data into the correct section of memory. It may sound like a piece of cake, but some terrible things can go wrong. Sometimes the display list is too long because you forgot that the first LMS instruction is one of the mode lines. The screen rolls or goes wacko. Maybe you let the display list inadvertently cross a 1K boundary, or allowed screen memory to cross a 4K boundary in the middle of a mode line. Each of these mistakes can cause the screen to behave erratically. If you do get a stable display, and it isn’t the one you specified, perhaps you forgot to tell ANTIC where either your display list or your RAM character set resides. It is possible that you didn’t place your character set on a 1K boundary, or on a 1/2K boundary if you are in GR. 1 or GR. 2. The fastest method to troubleshoot the problem in Assembly language is to enter the monitor and look at the intended areas for the display list and character set and to see if they are actually there. It is quite possible your memory move routine is faulty.

The next step is usually to initialize the starting positions of your players. Sometimes they just don’t appear, so you immediately check to see if the player shape is actually in the proper 256 bytes of player-missile memory. You should also check that the PMBASE is on a 2K boundary for singleline resolution players (1K boundary for double-line resolution), and that you told ANTIC where that is. If that isn’t the fault, some programmers make the mistake of trying to read a player’s horizontal position by looking at the ANTIC horizontal position register. You may be able to write a horizontal position to the hardware location, but you read collisions from these same hardware locations. If you are going to increment a player’s horizontal position, you will need to update a RAM location before writing the value into the hardware register. If this doesn’t appear to be the problem, there are two other possibilities. First, you may have forgotten to turn on player-missile graphics switches. But probably the most frequent mistake is to forget to set the player’s shadow color register. If it isn’t set, it defaults to the background color, blends in with the background and disappears. Always use the shadow color register to change or set color registers, or the change may only last one television frame because the hardware registers are updated every VBlank. The only exception to this rule is when you use a Display List Interrupt to change colors midscreen.

Display List and Vertical Blank Interrupts can sometimes cause unforeseen problems. Inexperience is usually the culprit. The first thing to remember is that you must have a program to interrupt from. Since it is easy to write a simple game entirely in Deferred Vertical Blank, the main loop can be as short as FOREVER JMP FOREVER. The machine will hang up if you don’t have somewhere to jump back to at the end of the VBI. On the other hand, if the code is too long, it will be interrupted by the next VBlank before it finishes. Unexpected results, such as a garbaged screen, may occur. The most common problems with Display List Interrupts occur when you forget to save your registers before entering the routine or forget to restore them before exiting. A mistake here will lock up the machine. The other problem is when the interrupt seems to occur on the wrong mode line. Remember that the interrupt has to be set on the mode line before the interrupt is to occur.

BASIC programmers who use Machine language subroutines sometimes encounter strange problems. If you are going to incorporate a VBlank routine, make sure you clear the decimal mode at the beginning. This is especially important if your program uses decimal arithmetic internally. Another problem occurs when you pull the incorrect number of bytes off the stack. This can lock up the machine on the return if the return address on the stack is incorrect. Unfortunately, these subroutines are very difficult to test in Assembly language without constructing a setup routine to simulate the stack environment.

BASIC is usually very forgiving, so it is unlikely that you will lock up the machine if you aren’t using Machine language subroutines. One of the most common display mistakes is forgetting to set a graphics mode after you lower RAMTOP to reserve space for your RAM character set and player-missile graphics. If you forget, you will still have a Graphics 0 display just below the old RAMTOP. The new graphics call will actually place the screen below RAMTOP.

We hope we have suggested adequate solutions for the most common errors that might occur in your games. We have learned many of these by bitter and frustrating experience. We will admit that these weren’t the only errors that we encountered when programming the code in this book. However, most of the others were logic problems that one of us alone couldn’t trace. For example, when I was programming the maze game, I programmed the manual mode for the joystick-controlled letter first. It worked fine, but became buggy when I added the auto mode. Sometimes the letter would behave properly, yet at other times it would escape the maze walls. I single-stepped the code repeatedly and the legal move flags were always set correctly. Days went by and I couldn’t find any cause for the anomaly. My partner discovered that it only happened just after the stick was returned to neutral. While legal moves were reset at the center of each maze block, moving the stick was required to close pathways other than those in the direction of movement or in reverse. Nothing was done in the neutral position because the letter was stopped in the non-auto mode. Since I had neglected to close gates when I was in the neutral position, the joystickcontrolled letter was now traveling in some direction automatically, so it became possible to give it a new direction command while it was between blocks. For example, if it had just passed a block that said it could go right, pushing right from the neutral position would command it to go right even though there was a wall there. In short, I forgot to close gates when I was in the auto mode, because I assumed they were set by one of the four non-neutral positions. This is a fine example of misguided thinking.

In closing, we hope that we have provided you with enough programming techniques and game theory to create your own arcade games. Remember that originality, persistence and attention to detail are the keys to success in this industry. We hope some of our readers will join the ranks of successful Atari game designers. If you take the easy way out and program a quick game, the results will show in mediocrity.（Source：atariarchives）