/*! pototskyy.net – "Architecture of Payment Systems" book page | Loaded only on pages that use the apsbook-* classes. */
.apsbook-section,.apsbook-section *{box-sizing:border-box}.apsbook-section{width:100vw !important;max-width:none !important;margin-left:calc(50% - 50vw) !important;margin-right:calc(50% - 50vw) !important;padding:80px 24px !important;border:0 !important}.apsbook-white{background:#ffffff !important;background-color:#ffffff !important}.apsbook-grey{background:#f4f6f8 !important;background-color:#f4f6f8 !important}.apsbook-dark{background:#17191c !important;background-color:#17191c !important;color:#ffffff !important}.apsbook-inner{width:100% !important;max-width:1120px !important;margin:0 auto !important}.apsbook-narrow{max-width:820px !important}.apsbook-section h1,.apsbook-section h2,.apsbook-section h3,.apsbook-section p,.apsbook-section ul{font-family:inherit !important}.apsbook-section h1{max-width:940px !important;margin:0 0 28px !important;padding:0 !important;font-size:clamp(46px,7vw,82px) !important;line-height:1.02 !important;font-weight:700 !important;letter-spacing:-0.045em !important}.apsbook-section h2{max-width:880px !important;margin:0 0 28px !important;padding:0 !important;font-size:clamp(32px,4vw,52px) !important;line-height:1.08 !important;font-weight:700 !important;letter-spacing:-0.03em !important}.apsbook-section h3{margin:0 0 12px !important;padding:0 !important;font-size:22px !important;line-height:1.3 !important;font-weight:700 !important}.apsbook-eyebrow{margin:0 0 18px !important;font-size:13px !important;line-height:1.4 !important;font-weight:700 !important;letter-spacing:0.11em !important;text-transform:uppercase !important;opacity:0.72}.apsbook-lead{max-width:850px !important;margin:0 0 28px !important;font-size:clamp(21px,2.3vw,28px) !important;line-height:1.45 !important;font-weight:400 !important}.apsbook-copy{max-width:820px !important}.apsbook-copy p{margin:0 0 22px !important;font-size:18px !important;line-height:1.72 !important}.apsbook-copy p:last-child{margin-bottom:0 !important}.apsbook-muted{opacity:0.7}.apsbook-status{display:inline-block !important;margin-top:10px !important;padding:9px 13px !important;border:1px solid #cdd2d7 !important;border-radius:3px !important;font-size:14px !important;line-height:1.4 !important;font-weight:600 !important}.apsbook-actions{display:flex !important;flex-wrap:wrap !important;gap:12px !important;margin-top:32px !important}.apsbook-btn{display:inline-block !important;padding:14px 22px !important;border:1px solid #17191c !important;border-radius:2px !important;text-decoration:none !important;font-size:16px !important;line-height:1.3 !important;font-weight:700 !important;transition:opacity .2s ease !important}.apsbook-btn:hover{opacity:0.75 !important}.apsbook-btn-primary{background:#17191c !important;color:#ffffff !important}.apsbook-btn-secondary{background:transparent !important;color:#17191c !important}.apsbook-dark .apsbook-btn-primary{background:#ffffff !important;color:#17191c !important;border-color:#ffffff !important}.apsbook-dark .apsbook-btn-secondary{color:#ffffff !important;border-color:#ffffff !important}.apsbook-grid{display:grid !important;grid-template-columns:repeat(2,minmax(0,1fr)) !important;gap:20px !important;margin-top:38px !important}.apsbook-grid-3{grid-template-columns:repeat(3,minmax(0,1fr)) !important}.apsbook-card{padding:28px !important;border:1px solid #d8dde2 !important;background:#ffffff !important;color:#17191c !important}.apsbook-card p{margin:0 !important;font-size:17px !important;line-height:1.65 !important}.apsbook-number{display:block !important;margin-bottom:24px !important;font-size:13px !important;font-weight:700 !important;letter-spacing:.1em !important;opacity:.55}.apsbook-question{max-width:900px !important;padding:23px 0 !important;border-bottom:1px solid #d4d8dd !important;font-size:21px !important;line-height:1.5 !important}.apsbook-question:first-child{border-top:1px solid #d4d8dd !important}.apsbook-part{margin-top:46px !important}.apsbook-part-label{margin:0 0 8px !important;font-size:13px !important;font-weight:700 !important;line-height:1.4 !important;letter-spacing:.09em !important;text-transform:uppercase !important;opacity:.6}.apsbook-list{margin:18px 0 0 !important;padding-left:23px !important}.apsbook-list li{margin-bottom:10px !important;font-size:18px !important;line-height:1.6 !important}.apsbook-note{margin-top:32px !important;padding:22px 24px !important;border-left:4px solid #17191c !important;background:#ffffff !important}.apsbook-note p{margin:0 !important;font-size:17px !important;line-height:1.65 !important}.apsbook-faq details{padding:22px 0 !important;border-bottom:1px solid #d4d8dd !important}.apsbook-faq summary{cursor:pointer !important;font-size:19px !important;line-height:1.4 !important;font-weight:700 !important}.apsbook-faq details p{max-width:800px !important;margin:16px 0 0 !important;font-size:17px !important;line-height:1.68 !important}@media (max-width:820px){.apsbook-section{padding:56px 20px !important}.apsbook-grid,.apsbook-grid-3{grid-template-columns:1fr !important}.apsbook-section h1{font-size:46px !important}.apsbook-section h2{font-size:34px !important}.apsbook-lead{font-size:22px !important}}@media (max-width:900px){.apsbook-hero-grid{grid-template-columns:1fr !important;gap:38px !important}.apsbook-hero-grid>div:last-child{max-width:520px}}.apsbook-dark,.apsbook-dark h1,.apsbook-dark h2,.apsbook-dark .apsbook-eyebrow,.apsbook-dark .apsbook-lead{color:#ffffff !important}.apsbook-top-form{padding:26px !important;background:#ffffff !important;border:1px solid #d8dde2 !important}.apsbook-top-form .fluentform{margin:0 !important}.apsbook-top-form .ff-el-group{margin-bottom:12px !important}.apsbook-top-form input[type="text"],.apsbook-top-form input[type="email"]{min-height:48px !important;padding:11px 14px !important;border:1px solid #cfd4d9 !important;border-radius:2px !important;background:#ffffff !important;font-size:16px !important}.apsbook-top-form .ff-btn-submit,.apsbook-top-form button[type="submit"]{width:100% !important;min-height:48px !important;padding:12px 20px !important;border:1px solid #17191c !important;border-radius:2px !important;background:#17191c !important;color:#ffffff !important;font-size:16px !important;font-weight:700 !important;cursor:pointer !important}.apsbook-top-form .ff-btn-submit:hover,.apsbook-top-form button[type="submit"]:hover{opacity:0.82 !important}.apsbook-top-form label{font-size:14px !important;font-weight:600 !important}.apsbook-top-form .ff-el-help-message,.apsbook-top-form .ff-el-form-check-label{font-size:13px !important;line-height:1.5 !important}@media (max-width:900px){.apsbook-subscribe-top-grid{grid-template-columns:1fr !important;gap:24px !important}}.apsbook-hero-grid{display:grid;grid-template-columns:minmax(0,1.45fr) minmax(320px,0.75fr);gap:56px;align-items:center}.apsbook-subscribe-top-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(320px,0.8fr);gap:48px;align-items:center}.apsbook-hero-media{width:100%}img.apsbook-cover{display:block;width:100%;max-width:460px;margin:0 auto;height:auto;aspect-ratio:4 / 5;object-fit:cover;object-position:center;border-radius:4px}.apsbook-btn.apsbook-btn--icon{display:inline-flex !important;align-items:center !important;gap:10px !important}.apsbook-btn--icon img{display:block !important;width:auto !important;height:22px !important}.apsbook-btn-secondary.apsbook-btn--icon img{height:18px !important}.apsbook-section.apsbook-section--compact{padding-top:34px !important;padding-bottom:34px !important}.apsbook-grid.apsbook-mt-34,.apsbook-note.apsbook-mt-34{margin-top:34px !important}.apsbook-actions.apsbook-mt-22{margin-top:22px !important}.apsbook-copy.apsbook-mt-30{margin-top:30px !important}.apsbook-section h2.apsbook-h2-compact{font-size:clamp(27px,3vw,40px) !important;margin-bottom:16px !important}.apsbook-copy p.apsbook-mb-0{margin-bottom:0 !important}
.apsbook-section h2.apsbook-eyebrow{max-width:none!important;margin:0 0 18px!important;padding:0!important;font-size:13px!important;line-height:1.4!important;font-weight:700!important;letter-spacing:0.11em!important;text-transform:uppercase!important}.apsbook-section p.apsbook-statement{max-width:880px!important;margin:0 0 28px!important;padding:0!important;font-size:clamp(32px,4vw,52px)!important;line-height:1.08!important;font-weight:700!important;letter-spacing:-0.03em!important}.apsbook-section p.apsbook-statement.apsbook-h2-compact{font-size:clamp(27px,3vw,40px)!important;margin-bottom:16px!important}@media (max-width:768px){.apsbook-section p.apsbook-statement{font-size:34px!important}}.apsbook-section p.apsbook-statement{color:var(--ast-global-color-2)!important}.apsbook-dark p.apsbook-statement{color:#ffffff!important}.apsbook-rail{position:fixed!important;top:50%!important;right:0!important;z-index:60!important;display:flex!important;flex-direction:column!important;gap:1px!important;transform:translateY(-50%)!important;border-radius:14px 0 0 14px!important;overflow:hidden!important;box-shadow:0 10px 30px rgba(0,0,0,0.22)!important}.apsbook-rail__item{display:flex!important;align-items:center!important;gap:10px!important;height:48px!important;max-width:48px!important;padding:0 14px!important;overflow:hidden!important;background:#17191c!important;color:#ffffff!important;text-decoration:none!important;white-space:nowrap!important;transition:max-width 0.25s ease,background-color 0.2s ease!important}.apsbook-rail__item:hover,.apsbook-rail__item:focus-visible{max-width:230px!important;background:#000000!important}.apsbook-rail__item:focus-visible{outline:2px solid #ffffff!important;outline-offset:-4px!important}.apsbook-rail__item svg{flex:0 0 20px!important;width:20px!important;height:20px!important}.apsbook-rail__label{font-size:14px!important;font-weight:600!important}#book-subscribe-top,#book-sponsor{scroll-margin-top:20px!important}@media (hover:none){.apsbook-rail__item:hover{max-width:48px!important}}@media (max-width:900px){.apsbook-rail{top:auto!important;bottom:96px!important;transform:none!important;opacity:0.94!important}.apsbook-rail__item,.apsbook-rail__item:hover{height:42px!important;max-width:42px!important;padding:0 11px!important}}@media (prefers-reduced-motion:reduce){.apsbook-rail__item{transition:none!important}}@media print{.apsbook-rail{display:none!important}}