:root {
    /* Light Mode Colors */
    --bg-primary: #f4f7f6;
    --bg-secondary: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --border-color: #dddddd;
    --nav-bg: #ffffff;
    --card-shadow: 0 8px 20px rgba(0,0,0,0.08);
    
    /* Modern Gradients */
    --primary-grad: linear-gradient(135deg, #6a11cb 0%, #2575fc 100%);
    --success-grad: linear-gradient(135deg, #11998e 0%, #38ef7d 100%);
    --warning-grad: linear-gradient(135deg, #f6d365 0%, #fda085 100%);
    --danger-grad: linear-gradient(135deg, #ff0844 0%, #ffb199 100%);
    --table-header: #f8f9fa;
}

[data-theme="dark"] {
    --bg-primary: #121212;
    --bg-secondary: #1e1e1e;
    --text-primary: #f0f0f0;
    --text-secondary: #aaaaaa;
    --border-color: #333333;
    --nav-bg: #1a1a1a;
    --card-shadow: 0 8px 20px rgba(0,0,0,0.5);
    --table-header: #2c2c2c;
}

* { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; }

body { background-color: var(--bg-primary); color: var(--text-primary); transition: 0.3s; }

.navbar { background-color: var(--nav-bg); padding: 15px 30px; display: flex; justify-content: space-between; align-items: center; box-shadow: 0 2px 10px rgba(0,0,0,0.1); }
.container { padding: 30px; max-width: 1000px; margin: 0 auto; }

button { cursor: pointer; border: none; border-radius: 6px; font-weight: bold; transition: all 0.3s ease; letter-spacing: 0.5px; }
button:hover { transform: translateY(-2px); box-shadow: 0 5px 15px rgba(0,0,0,0.2); }

.primary-btn { background: var(--primary-grad); color: white; padding: 12px 20px; width: 100%; }
.success-btn { background: var(--success-grad); color: white; padding: 10px 15px; }
.danger-btn { background: var(--danger-grad); color: white; padding: 10px 15px; }
.info-btn { background: var(--primary-grad); color: white; padding: 8px 10px; flex: 1; }
.warning-btn { background: var(--warning-grad); color: #fff; padding: 8px 10px; flex: 1; text-shadow: 0 1px 2px rgba(0,0,0,0.2); }
.secondary-btn { background: #6c757d; color: white; padding: 8px 15px; }

.class-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 20px; margin-top: 20px; }
.class-card { background: var(--bg-secondary); padding: 25px; border-radius: 12px; border: 1px solid var(--border-color); box-shadow: var(--card-shadow); transition: 0.3s; }
.class-card h4 { color: var(--text-primary); font-size: 20px; margin-bottom: 10px; }
.class-card p { margin-bottom: 15px; font-size: 14px; color: var(--text-secondary); }

.data-table { width: 100%; border-collapse: collapse; background: var(--bg-secondary); margin-top: 15px; border-radius: 8px; overflow: hidden; box-shadow: var(--card-shadow); }
.data-table th, .data-table td { padding: 15px; border-bottom: 1px solid var(--border-color); text-align: left; }
.data-table th { background-color: var(--table-header); color: var(--text-primary); }

input, .edit-input, .input-box { width: 100%; padding: 12px; border: 1px solid var(--border-color); border-radius: 6px; background: var(--bg-primary); color: var(--text-primary); transition: 0.3s; }
input:focus { outline: none; border-color: #6a11cb; box-shadow: 0 0 5px rgba(106, 17, 203, 0.3); }

.theme-toggle { position: fixed; bottom: 30px; right: 30px; background: var(--primary-grad); color: white; border: none; border-radius: 50%; width: 55px; height: 55px; font-size: 24px; cursor: pointer; box-shadow: 0 4px 15px rgba(0,0,0,0.3); z-index: 9999; display: flex; justify-content: center; align-items: center; }