/* ===================================================================
   Style.css (Corrected & Optimized Version)
   Author: Keshab Sarkar
   Project: Physics Study App
   =================================================================== */

/* --- 1. Settings, Fonts & Variables (সেটিংস, ফন্ট ও ভেরিয়েবল) --- */

@import url('https://fonts.googleapis.com/css2?family=Hind+Siliguri:wght@400;500;600;700&display=swap');

:root {
    /* Day Mode Colors */
    --bg-day: #f4f7f9;
    --card-bg-day: #ffffff;
    --text-color-day: #34495e;
    --heading-color-day: #2c3e50;
    --border-color-day: #e5eaee;
    --accent-color-day: #3498db;
    --accent-color-light-day: #eaf4fb;
    --hover-darken-day: #2980b9; /* Accent color এর গাঢ় শেড */
    
    /* Dark Mode Colors */
    --bg-dark: #121212;
    --card-bg-dark: #1e1e1e;
    --text-color-dark: #e0e0e0;
    --heading-color-dark: #ffffff;
    --border-color-dark: #333;
    --accent-color-dark: #5dade2;
    --accent-color-light-dark: #2c3e50;
    --hover-darken-dark: #8ecae6; /* ডার্ক মোডের জন্য Accent color এর হালকা শেড */
}

/* --- 2. Global & Body Styles (গ্লোবাল ও বডি স্টাইল) --- */

body {
    font-family: 'Hind Siliguri', sans-serif;
    margin: 0;
    padding: 20px;
    transition: background-color 0.4s, color 0.4s;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Day & Dark Mode Theming */
body.day-mode {
    background-color: var(--bg-day);
    color: var(--text-color-day);
    --card-bg: var(--card-bg-day);
    --text-color: var(--text-color-day);
    --heading-color: var(--heading-color-day);
    --border-color: var(--border-color-day);
    --accent-color: var(--accent-color-day);
    --accent-color-light: var(--accent-color-light-day);
    --hover-darken: var(--hover-darken-day);
}
body.dark-mode {
    background-color: var(--bg-dark);
    color: var(--text-color-dark);
    --card-bg: var(--card-bg-dark);
    --text-color: var(--text-color-dark);
    --heading-color: var(--heading-color-dark);
    --border-color: var(--border-color-dark);
    --accent-color: var(--accent-color-dark);
    --accent-color-light: var(--accent-color-light-dark);
    --hover-darken: var(--hover-darken-dark);
}

.homepage {
    max-width: 900px;
    margin: 0 auto;
}

/* --- 3. Utility Components (ইউটিলিটি কম্পোনেন্ট) --- */

#preloader { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: var(--card-bg); z-index: 1001; display: flex; justify-content: center; align-items: center; }
.loader { border: 8px solid rgba(0,0,0,0.1); border-top: 8px solid var(--accent-color); border-radius: 50%; width: 60px; height: 60px; animation: spin 1s linear infinite; }
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }

.dark-mode-button { position: absolute; top: 20px; right: 0; background: var(--card-bg); border: 1px solid var(--border-color); width: 45px; height: 45px; border-radius: 50%; display: flex; justify-content: center; align-items: center; cursor: pointer; font-size: 1.2rem; color: var(--text-color); transition: all 0.3s; }
.dark-mode-button:hover { transform: scale(1.1) rotate(15deg); background-color: var(--accent-color-light); }

#back-to-top { display: none; position: fixed; bottom: 20px; right: 20px; background: var(--accent-color); color: white; width: 50px; height: 50px; border-radius: 50%; text-decoration: none; text-align: center; line-height: 50px; font-size: 1.5rem; z-index: 1000; box-shadow: 0 4px 10px rgba(0,0,0,0.2); transition: background-color 0.3s, transform 0.3s; }
#back-to-top:hover { transform: translateY(-3px); }

/* --- 4. Header & Navigation (হেডার ও নেভিগেশন) --- */

.main-header { display: flex; flex-direction: column; align-items: center; text-align: center; padding: 20px 0; position: relative; }
.profile-pic { width: 120px; height: 120px; border-radius: 50%; object-fit: cover; border: 5px solid white; box-shadow: 0 4px 15px rgba(0,0,0,0.1); }
.header-text h1 { font-size: 2.5rem; margin: 15px 0 5px; color: var(--heading-color); }
.header-text p { font-size: 1.1rem; margin: 0; color: var(--text-color); opacity: 0.8; }

.search-container { margin: 20px 0; position: relative; }
.search-container i { position: absolute; left: 15px; top: 50%; transform: translateY(-50%); color: #9ca3af; }
#search-bar { width: 100%; padding: 12px 12px 12px 45px; font-size: 1rem; border: 1px solid var(--border-color); border-radius: 8px; background-color: var(--card-bg); color: var(--text-color); transition: all 0.3s; }
#search-bar:focus { outline: none; border-color: var(--accent-color); box-shadow: 0 0 0 3px var(--accent-color-light); }
body.dark-mode #search-bar:focus { box-shadow: 0 0 0 3px rgba(93, 173, 226, 0.3); }

.nav-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); gap: 15px; margin: 30px 0; }
.nav-button { color: white; text-decoration: none; padding: 20px; border-radius: 12px; display: flex; flex-direction: column; align-items: center; justify-content: center; text-align: center; transition: transform 0.2s ease, box-shadow 0.2s ease; border: none; font-size: 1rem; cursor: pointer; }
.nav-button:hover { transform: translateY(-5px); box-shadow: 0 8px 20px rgba(0,0,0,0.1); }
.nav-button i { font-size: 2rem; margin-bottom: 10px; }
.nav-button span { font-weight: 600; font-size: 1rem; }

.nav-button.color-home { background: linear-gradient(135deg, #ff7e5f, #feb47b); }
.nav-button.color-dashboard { background: linear-gradient(45deg, #4e54c8, #8f94fb); }
.nav-button.color-notes { background: linear-gradient(45deg, #16a085, #1abc9c); }
.nav-button.color-quiz { background: linear-gradient(45deg, #d35400, #e67e22); }
.nav-button.color-formulas { background: linear-gradient(45deg, #f39c12, #f1c40f); }
.nav-button.color-leaderboard { background: linear-gradient(45deg, #8e44ad, #9b59b6); }

/* --- 5. Main Content & Cards (মূল কন্টেন্ট ও কার্ড) --- */

main { display: flex; flex-direction: column; gap: 30px; }
.card { background: var(--card-bg); padding: 30px; border-radius: 15px; border: 1px solid var(--border-color); box-shadow: 0 4px 10px rgba(0,0,0,0.05); }
.card h2 { font-size: 1.8rem; color: var(--heading-color); margin-top: 0; display: flex; align-items: center; gap: 10px; }
.icon-title { color: var(--accent-color); }
.card p { margin: 10px 0 20px; line-height: 1.6; }
.link-container { display: flex; flex-wrap: wrap; gap: 10px; }
.link-container a { background: var(--accent-color); color: white; text-decoration: none; padding: 10px 18px; border-radius: 25px; font-weight: 500; transition: background-color 0.2s, transform 0.2s; }
.link-container a:hover { background: var(--hover-darken); transform: translateY(-2px); }

/* --- 6. Page-Specific Sections (পেজ-ভিত্তিক সেকশন) --- */

/* User Profile */
#user-profile-card .profile-header { display: flex; align-items: center; gap: 20px; }
.profile-pic-large { width: 80px; height: 80px; border-radius: 50%; object-fit: cover; }
#user-profile-card h2 { margin: 0; font-size: 1.5rem; }
#user-profile-card p { margin: 5px 0 0; color: #7f8c8d; }

/* Dashboard */
.dashboard-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.5rem; }
.dashboard-item { text-align: center; padding: 1.5rem; background-color: var(--card-bg); border: 1px solid var(--border-color); border-radius: 12px; }
.dashboard-item h3 { margin-top: 0; font-size: 1.2rem; color: var(--heading-color); }
.progress-bar-container { width: 100%; background-color: #e0e0e0; border-radius: 30px; margin: 1rem 0; overflow: hidden; }
body.dark-mode .progress-bar-container { background-color: #444; }
.progress-bar { height: 20px; width: 0%; background-color: #27ae60; border-radius: 30px; transition: width 1s ease-in-out; }
#chapter-progress-text { font-weight: 600; color: var(--text-color); }
.challenge-box { background-color: var(--card-bg); border: 2px dashed var(--accent-color); padding: 1rem; border-radius: 8px; margin-top: 1rem; }
.achievements-container { display: flex; flex-wrap: wrap; justify-content: center; gap: 15px; margin-top: 1rem; }
.achievement-badge { display: flex; flex-direction: column; align-items: center; width: 80px; text-align: center; opacity: 0.4; filter: grayscale(100%); transition: all 0.4s; }
.achievement-badge.unlocked { opacity: 1; filter: grayscale(0%); transform: scale(1.1); }
.achievement-badge i { font-size: 2.5rem; color: #f1c40f; }
.achievement-badge span { font-size: 0.8rem; font-weight: 600; margin-top: 5px; }

/* Leaderboard */
.leaderboard-container { margin-top: 1.5rem; overflow-x: auto; }
table { width: 100%; border-collapse: collapse; text-align: left; }
th, td { padding: 12px 15px; border-bottom: 1px solid var(--border-color); vertical-align: middle; }
thead { background-color: var(--accent-color-light); }
body.dark-mode thead { background-color: #2d3748; }
td i.fa-trophy, td i.fa-medal { margin-right: 8px; font-size: 1.2em; }

/* Leaderboard Dropdown Styles */
.toggle-details-btn { background: none; border: none; color: var(--accent-color); cursor: pointer; font-size: 1.2rem; padding: 5px; transition: transform 0.3s ease; }
.toggle-details-btn.open { transform: rotate(180deg); }
.details-row { display: none; }
.details-content { background-color: var(--accent-color-light); padding: 15px; border-left: 4px solid var(--accent-color); }
body.dark-mode .details-content { background-color: #2c2c2c; }
.details-content ul { list-style-type: none; padding-left: 0; margin: 0; }
.details-content li { margin-bottom: 8px; font-size: 0.9em; }
.details-content li .label { font-weight: bold; color: #555; }
body.dark-mode .details-content li .label { color: #bbb; }

/* Corrected Note Cards Styling */
.notes-grid-container { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 15px; margin-top: 20px; }
.note-card { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 10px; padding: 20px; background-color: var(--accent-color-light); border: 1px solid var(--border-color); border-radius: 12px; text-decoration: none; color: var(--text-color); font-weight: 500; text-align: center; transition: all 0.3s ease; }
.note-card i { font-size: 2rem; color: var(--accent-color); }
.note-card:hover { transform: translateY(-5px); box-shadow: 0 6px 12px rgba(0, 0, 0, 0.1); background-color: var(--accent-color); color: white; }
.note-card:hover i { color: white; } /* হোভার করলে আইকনের রঙও সাদা হবে */


/* --- 7. Modals (মোডাল) --- */

.modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background-color: rgba(0,0,0,0.7); z-index: 1001; display: none; justify-content: center; align-items: center; backdrop-filter: blur(4px); }
.modal-overlay.active { display: flex; }
.modal-content { background-color: var(--card-bg); padding: 2rem; border-radius: 12px; width: 90%; max-width: 500px; position: relative; box-shadow: 0 5px 20px rgba(0,0,0,0.3); text-align: center; }
.modal-close-btn { position: absolute; top: 10px; right: 20px; background: none; border: none; font-size: 2rem; cursor: pointer; color: var(--text-color); }
.modal-content h2 { margin-top: 0; color: var(--heading-color); }
.modal-content ul { list-style: none; padding: 0; text-align: left; }
.modal-content li { padding: 12px 0; font-size: 1.1rem; border-bottom: 1px dashed var(--border-color); }
.modal-content li:last-child { border-bottom: none; }

/* --- 8. Footer (ফুটার) --- */

footer { text-align: center; padding: 30px 0; margin-top: 30px; border-top: 1px solid var(--border-color); }
.social-links a { margin: 0 10px; color: var(--text-color); font-size: 1.2rem; transition: color 0.3s, transform 0.3s; display: inline-block; }
.social-links a:hover { color: var(--accent-color); transform: translateY(-3px); }

/* --- 9. Responsive Design (রেসপন্সিভ ডিজাইন) --- */

@media (max-width: 768px) {
    .nav-grid { grid-template-columns: repeat(3, 1fr); }
    #user-profile-card .profile-header { flex-direction: column; text-align: center; }
}

@media (max-width: 480px) {
    body { padding: 15px; }
    .header-text h1 { font-size: 2rem; }
    .nav-grid { grid-template-columns: repeat(2, 1fr); }
    .card { padding: 20px; }
    .dark-mode-button { top: 10px; right: 10px; }
}