:root{--primary-bg: #f4f7f6;--card-bg: #ffffff;--text-color: #333;--header-bg: #ffffff;--shadow-color: rgba(0, 0, 0, .1);--accent-color-1: #4e54c8;--font-family: "Poppins", sans-serif;--header-height: 60px}*{box-sizing:border-box;margin:0;padding:0}body{font-family:var(--font-family);background-color:var(--primary-bg);color:var(--text-color);overscroll-behavior:none}#root{max-width:100vw;min-height:100vh}.app-container{display:flex;flex-direction:column;min-height:100vh}.header{display:flex;justify-content:space-between;align-items:center;padding:1rem 1.5rem;background-color:var(--header-bg);box-shadow:0 2px 8px var(--shadow-color);position:sticky;top:0;z-index:100;min-height:var(--header-height)}.app-title{font-size:1.5rem;font-weight:700;color:var(--accent-color-1)}.back-button{background:none;border:none;cursor:pointer;color:var(--text-color);display:flex;flex-direction:column;align-items:center;justify-content:center;padding:0;font-family:inherit}.back-button-arrow{font-size:2.2rem;font-weight:700;line-height:1}.back-button-text{font-size:.65rem;margin-top:-2px;font-weight:500;color:#555}.menu-button{background:none;border:none;cursor:pointer;z-index:102;width:30px;height:22px;display:flex;flex-direction:column;justify-content:space-between}.menu-button span{display:block;width:100%;height:3px;background-color:var(--text-color);border-radius:3px;transition:all .3s ease-in-out}.menu-overlay{position:fixed;top:var(--header-height);left:0;width:100%;height:calc(100% - var(--header-height));background-color:#00000080;z-index:100;opacity:0;visibility:hidden;transition:opacity .3s ease,visibility .3s ease}.menu-overlay.open{opacity:1;visibility:visible}.menu-panel{position:fixed;top:var(--header-height);left:-300px;width:250px;height:calc(100% - var(--header-height));background-color:#fff;z-index:101;padding:2rem 1.5rem;transition:left .3s ease-in-out;box-shadow:4px 0 20px #0000001a;border-right:1px solid #ddd}.menu-panel.open{left:0}.menu-panel ul{list-style:none}.menu-panel li{margin-bottom:1rem}.menu-panel a{display:block;padding:12px 20px;text-decoration:none;color:#333;font-size:1.1rem;font-weight:500;cursor:pointer;border-radius:10px;background-color:#f4f7f6;border:1px solid #e0e0e0;text-align:center;transition:all .2s ease-in-out}.menu-panel a:hover,.menu-panel a:focus{background-image:linear-gradient(135deg,#667eea,#764ba2);color:#fff;transform:translateY(-3px);box-shadow:0 6px 12px #00000026;border-color:transparent}.main-content{padding:2rem;flex-grow:1}.screen-title{font-size:2rem;font-weight:600;margin-bottom:2rem;text-align:center;color:#2c3e50}.home-subtitle{font-size:1.25rem;font-weight:500;margin-top:1rem;margin-bottom:2rem;text-align:center;color:#34495e;padding:0 1rem}.card-list{display:grid;grid-template-columns:1fr;gap:1.5rem}@media (min-width: 600px){.card-list{grid-template-columns:repeat(2,1fr)}}@media (min-width: 900px){.card-list{grid-template-columns:repeat(3,1fr)}}.card{background:var(--card-bg);border-radius:16px;padding:1.25rem 2rem;text-align:center;box-shadow:0 4px 15px var(--shadow-color);cursor:pointer;transition:transform .3s ease,box-shadow .3s ease;border:1px solid #e0e0e0;display:flex;flex-direction:column;justify-content:center;align-items:center;min-height:100px}.card:hover{transform:translateY(-5px);box-shadow:0 8px 25px #00000026}.card h3{font-size:1.5rem;font-weight:600;margin:0}.card.color-1{background-image:linear-gradient(135deg,#fce38a,#f38181);color:#fff}.card.color-2{background-image:linear-gradient(135deg,#96fbc4,#f9f586);color:#333}.card.color-3{background-image:linear-gradient(135deg,#84fab0,#8fd3f4);color:#333}.card.color-4{background-image:linear-gradient(135deg,#a1c4fd,#c2e9fb);color:#333}.card.color-5{background-image:linear-gradient(135deg,#ff9a9e,#fecfef);color:#333}.card.color-6{background-image:linear-gradient(135deg,#d4fc79,#96e6a1);color:#333}.notes-container{background:var(--card-bg);border-radius:16px;padding:2rem;box-shadow:0 4px 15px var(--shadow-color);line-height:1.8}.notes-placeholder{font-size:1.2rem;color:#777;text-align:center;min-height:200px;display:flex;justify-content:center;align-items:center}.notes-content{color:#34495e;font-size:1.1rem}.notes-content h2,.notes-content h3{font-weight:700;margin-top:2rem;margin-bottom:1rem;padding:.5rem 1rem;border-radius:8px;color:#fff}.notes-content h2{font-size:1.8rem;background:linear-gradient(135deg,#667eea,#764ba2)}.notes-content h3{font-size:1.5rem;background:linear-gradient(135deg,#43e97b,#38f9d7);color:#333}.notes-content p{margin-bottom:1rem}.notes-content strong{color:#c0392b;font-weight:600}.notes-content ul{list-style-position:inside;padding-left:1rem;margin-bottom:1rem}.notes-content li{margin-bottom:.5rem}.notes-content .definition,.notes-content .example,.notes-content .reaction,.notes-content .formula{padding:1rem;margin:1.5rem 0;border-left-width:5px;border-left-style:solid;border-radius:5px;background-color:#f8f9fa}.notes-content .definition{border-color:#3498db}.notes-content .example{border-color:#2ecc71}.notes-content .reaction{border-color:#e67e22}.notes-content .formula{border-color:#9b59b6}.notes-content .definition strong,.notes-content .example strong{color:#2c3e50}.notes-content table{width:100%;border-collapse:collapse;margin:2rem 0;box-shadow:0 2px 10px #0000001a;border-radius:8px;overflow:hidden}.notes-content th,.notes-content td{padding:12px 15px;text-align:left;border-bottom:1px solid #ddd}.notes-content th{background-color:#4e54c8;color:#fff;font-weight:600}.notes-content tr:nth-child(2n){background-color:#f2f2f2}.notes-content tr:hover{background-color:#e9e9ff}.table-responsive-wrapper{width:100%;overflow-x:auto;-webkit-overflow-scrolling:touch}.table-responsive-wrapper>table{min-width:600px}.main-content.chapter-view{padding:1.5rem 0}.chapter-view .screen-title{padding:0 1.5rem;margin-top:0;margin-bottom:1.5rem;font-size:1.8rem}.chapter-view .notes-container{background:transparent;border-radius:0;box-shadow:none;padding:0 1.5rem}