:root {
    --bg-color: #f0f2f5;
    --container-bg: #ffffff;
    --text-color: #2c3e50;
    --primary-color: #2c3e50;
    --primary-hover: #1a252f;
    --accent-color: #1abc9c;
    --error-bg: #fdecea;
    --error-text: #c0392b;
    --result-bg: #e8f8f5;
    --border-color: #bdc3c7;
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --container-bg: #2d2d2d;
    --text-color: #ecf0f1;
    --primary-color: #34495e;
    --primary-hover: #2c3e50;
    --accent-color: #16a085;
    --error-bg: #4a2323;
    --error-text: #ff7675;
    --result-bg: #1e3c36;
    --border-color: #444;
}

body { font-family: 'Segoe UI', Arial, sans-serif; margin: 0; padding: 20px; background: var(--bg-color); color: var(--text-color); transition: background 0.3s, color 0.3s; }
.container { max-width: 1200px; margin: 0 auto; background: var(--container-bg); padding: 25px; border-radius: 12px; box-shadow: 0 5px 20px rgba(0,0,0,0.1); }
.header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; }
.theme-toggle { background: none; border: 1px solid var(--border-color); color: var(--text-color); padding: 8px 12px; border-radius: 6px; cursor: pointer; }

.tabs { display: flex; gap: 10px; margin-bottom: 20px; border-bottom: 2px solid var(--border-color); }
.tab { padding: 10px 20px; cursor: pointer; border-bottom: 3px solid transparent; font-weight: bold; color: var(--text-color); opacity: 0.7; }
.tab.active { border-bottom-color: var(--accent-color); opacity: 1; }
.tab-content { display: none; }
.tab-content.active { display: block; }

.form-group { margin-bottom: 15px; }
label { display: block; font-weight: 600; margin-bottom: 6px; font-size: 0.9em; }
input, select, textarea { width: 100%; padding: 10px; border: 1px solid var(--border-color); border-radius: 6px; background: var(--container-bg); color: var(--text-color); box-sizing: border-box; }
input:focus, select:focus { outline: none; border-color: var(--accent-color); }

button, .btn { background: var(--primary-color); color: white; padding: 10px 18px; border: none; border-radius: 6px; cursor: pointer; margin-right: 10px; margin-top: 10px; font-size: 1em; }
button:hover, .btn:hover { background: var(--primary-hover); }
.btn-secondary { background: #7f8c8d; }
.btn-danger { background: #e74c3c; }

.result-box { background: var(--result-bg); border-left: 5px solid var(--accent-color); padding: 15px; border-radius: 8px; margin: 20px 0; display: none; }
.result-box.visible { display: block; animation: fadeIn 0.5s; }
.error-box { background: var(--error-bg); border-left: 5px solid var(--error-text); padding: 15px; border-radius: 8px; color: var(--error-text); margin: 20px 0; display: none; }

.history-controls { display: flex; gap: 10px; margin-bottom: 15px; flex-wrap: wrap; align-items: flex-end; }
.history-controls .form-group { margin-bottom: 0; flex: 1; min-width: 150px; }

table { width: 100%; border-collapse: collapse; margin-top: 15px; font-size: 0.9em; }
th, td { border: 1px solid var(--border-color); padding: 10px; text-align: left; }
th { background: rgba(0,0,0,0.05); }

@keyframes fadeIn { from { opacity: 0; transform: translateY(-10px); } to { opacity: 1; transform: translateY(0); } }
.fields-group { background: rgba(0,0,0,0.03); padding: 15px; border-radius: 8px; margin-top: 10px; border: 1px solid var(--border-color); display: none; }
.fields-group.visible { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 15px; }
.chart-container { max-width: 400px; margin: 20px auto; }